FM / library

/usr/share/doc/python2-docs/html/_sources/library/

/usr/share/doc/python2-docs/html/_sources/library

Name	Size	Mode	Actions
2to3.rst.txt	14647	0644	edit dl rm
abc.rst.txt	7219	0644	edit dl rm
aepack.rst.txt	4257	0644	edit dl rm
aetools.rst.txt	3532	0644	edit dl rm
aetypes.rst.txt	4257	0644	edit dl rm
aifc.rst.txt	7086	0644	edit dl rm
al.rst.txt	5309	0644	edit dl rm
allos.rst.txt	695	0644	edit dl rm
anydbm.rst.txt	4111	0644	edit dl rm
archiving.rst.txt	424	0644	edit dl rm
argparse.rst.txt	74685	0644	edit dl rm
array.rst.txt	10524	0644	edit dl rm
ast.rst.txt	10111	0644	edit dl rm
asynchat.rst.txt	9206	0644	edit dl rm
asyncore.rst.txt	12937	0644	edit dl rm
atexit.rst.txt	3910	0644	edit dl rm
audioop.rst.txt	10395	0644	edit dl rm
autogil.rst.txt	1015	0644	edit dl rm
base64.rst.txt	6252	0644	edit dl rm
basehttpserver.rst.txt	10404	0644	edit dl rm
bastion.rst.txt	2611	0644	edit dl rm
bdb.rst.txt	12456	0644	edit dl rm
binascii.rst.txt	6508	0644	edit dl rm
binhex.rst.txt	1910	0644	edit dl rm
bisect.rst.txt	5415	0644	edit dl rm
bsddb.rst.txt	7575	0644	edit dl rm
bz2.rst.txt	8064	0644	edit dl rm
calendar.rst.txt	11282	0644	edit dl rm
carbon.rst.txt	15956	0644	edit dl rm
cd.rst.txt	11974	0644	edit dl rm
cgi.rst.txt	22853	0644	edit dl rm
cgihttpserver.rst.txt	2788	0644	edit dl rm
cgitb.rst.txt	2874	0644	edit dl rm
chunk.rst.txt	4955	0644	edit dl rm
cmath.rst.txt	7647	0644	edit dl rm
cmd.rst.txt	8565	0644	edit dl rm
code.rst.txt	7115	0644	edit dl rm
codecs.rst.txt	66966	0644	edit dl rm
codeop.rst.txt	3774	0644	edit dl rm
collections.rst.txt	41448	0644	edit dl rm
colorpicker.rst.txt	913	0644	edit dl rm
colorsys.rst.txt	1819	0644	edit dl rm
commands.rst.txt	2595	0644	edit dl rm
compileall.rst.txt	4678	0644	edit dl rm
compiler.rst.txt	37464	0644	edit dl rm
configparser.rst.txt	19607	0644	edit dl rm
constants.rst.txt	2328	0644	edit dl rm
contextlib.rst.txt	6012	0644	edit dl rm
cookie.rst.txt	9543	0644	edit dl rm
cookielib.rst.txt	27875	0644	edit dl rm
copy.rst.txt	3351	0644	edit dl rm
copy_reg.rst.txt	2329	0644	edit dl rm
crypt.rst.txt	2292	0644	edit dl rm
crypto.rst.txt	355	0644	edit dl rm
csv.rst.txt	22757	0644	edit dl rm
ctypes.rst.txt	90513	0644	edit dl rm
curses.ascii.rst.txt	9046	0644	edit dl rm
curses.panel.rst.txt	2740	0644	edit dl rm
curses.rst.txt	74877	0644	edit dl rm
custominterp.rst.txt	570	0644	edit dl rm
datatypes.rst.txt	864	0644	edit dl rm
datetime.rst.txt	74679	0644	edit dl rm
dbhash.rst.txt	3865	0644	edit dl rm
dbm.rst.txt	3117	0644	edit dl rm
debug.rst.txt	446	0644	edit dl rm
decimal.rst.txt	70926	0644	edit dl rm
development.rst.txt	640	0644	edit dl rm
difflib.rst.txt	30716	0644	edit dl rm
dircache.rst.txt	1813	0644	edit dl rm
dis.rst.txt	23248	0644	edit dl rm
distribution.rst.txt	426	0644	edit dl rm
distutils.rst.txt	1958	0644	edit dl rm
dl.rst.txt	3392	0644	edit dl rm
doctest.rst.txt	73985	0644	edit dl rm
docxmlrpcserver.rst.txt	3802	0644	edit dl rm
dumbdbm.rst.txt	2841	0644	edit dl rm
dummy_thread.rst.txt	1058	0644	edit dl rm
dummy_threading.rst.txt	799	0644	edit dl rm
easydialogs.rst.txt	10346	0644	edit dl rm
email-examples.rst.txt	1271	0644	edit dl rm
email.charset.rst.txt	9654	0644	edit dl rm
email.encoders.rst.txt	2376	0644	edit dl rm
email.errors.rst.txt	4006	0644	edit dl rm
email.generator.rst.txt	6132	0644	edit dl rm
email.header.rst.txt	7531	0644	edit dl rm
email.iterators.rst.txt	2421	0644	edit dl rm
email.message.rst.txt	25217	0644	edit dl rm
email.mime.rst.txt	9917	0644	edit dl rm
email.parser.rst.txt	10327	0644	edit dl rm
email.rst.txt	16111	0644	edit dl rm
email.utils.rst.txt	6475	0644	edit dl rm
ensurepip.rst.txt	5022	0644	edit dl rm
errno.rst.txt	6708	0644	edit dl rm
exceptions.rst.txt	18343	0644	edit dl rm
fcntl.rst.txt	7361	0644	edit dl rm
filecmp.rst.txt	5348	0644	edit dl rm
fileformats.rst.txt	302	0644	edit dl rm
fileinput.rst.txt	7417	0644	edit dl rm
filesys.rst.txt	806	0644	edit dl rm
fl.rst.txt	17646	0644	edit dl rm
fm.rst.txt	2699	0644	edit dl rm
fnmatch.rst.txt	3104	0644	edit dl rm
formatter.rst.txt	13245	0644	edit dl rm
fpectl.rst.txt	4171	0644	edit dl rm
fpformat.rst.txt	1747	0644	edit dl rm
fractions.rst.txt	5297	0644	edit dl rm
framework.rst.txt	11444	0644	edit dl rm
frameworks.rst.txt	378	0644	edit dl rm
ftplib.rst.txt	15720	0644	edit dl rm
functions.rst.txt	75554	0644	edit dl rm
functools.rst.txt	7448	0644	edit dl rm
future_builtins.rst.txt	2010	0644	edit dl rm
gc.rst.txt	9014	0644	edit dl rm
gdbm.rst.txt	4882	0644	edit dl rm
gensuitemodule.rst.txt	3113	0644	edit dl rm
getopt.rst.txt	6670	0644	edit dl rm
getpass.rst.txt	1876	0644	edit dl rm
gettext.rst.txt	29040	0644	edit dl rm
gl.rst.txt	6009	0644	edit dl rm
glob.rst.txt	2414	0644	edit dl rm
grp.rst.txt	2256	0644	edit dl rm
gzip.rst.txt	4828	0644	edit dl rm
hashlib.rst.txt	7379	0644	edit dl rm
heapq.rst.txt	13185	0644	edit dl rm
hmac.rst.txt	3073	0644	edit dl rm
hotshot.rst.txt	4289	0644	edit dl rm
htmllib.rst.txt	7379	0644	edit dl rm
htmlparser.rst.txt	11640	0644	edit dl rm
httplib.rst.txt	37454	0644	edit dl rm
i18n.rst.txt	409	0644	edit dl rm
ic.rst.txt	5005	0644	edit dl rm
idle.rst.txt	22182	0644	edit dl rm
imageop.rst.txt	4001	0644	edit dl rm
imaplib.rst.txt	17221	0644	edit dl rm
imgfile.rst.txt	2765	0644	edit dl rm
imghdr.rst.txt	2635	0644	edit dl rm
imp.rst.txt	12593	0644	edit dl rm
importlib.rst.txt	1126	0644	edit dl rm
imputil.rst.txt	7023	0644	edit dl rm
index.rst.txt	2287	0644	edit dl rm
inspect.rst.txt	28151	0644	edit dl rm
internet.rst.txt	950	0644	edit dl rm
intro.rst.txt	2803	0644	edit dl rm
io.rst.txt	39015	0644	edit dl rm
ipc.rst.txt	630	0644	edit dl rm
itertools.rst.txt	36324	0644	edit dl rm
jpeg.rst.txt	3858	0644	edit dl rm
json.rst.txt	25545	0644	edit dl rm
keyword.rst.txt	617	0644	edit dl rm
language.rst.txt	523	0644	edit dl rm
linecache.rst.txt	1887	0644	edit dl rm
locale.rst.txt	24975	0644	edit dl rm
logging.config.rst.txt	31560	0644	edit dl rm
logging.handlers.rst.txt	28153	0644	edit dl rm
logging.rst.txt	46882	0644	edit dl rm
mac.rst.txt	791	0644	edit dl rm
macos.rst.txt	3824	0644	edit dl rm
macosa.rst.txt	3964	0644	edit dl rm
macostools.rst.txt	4017	0644	edit dl rm
macpath.rst.txt	650	0644	edit dl rm
mailbox.rst.txt	68129	0644	edit dl rm
mailcap.rst.txt	3675	0644	edit dl rm
markup.rst.txt	1249	0644	edit dl rm
marshal.rst.txt	5689	0644	edit dl rm
math.rst.txt	10920	0644	edit dl rm
md5.rst.txt	2815	0644	edit dl rm
mhlib.rst.txt	3966	0644	edit dl rm
mimetools.rst.txt	4504	0644	edit dl rm
mimetypes.rst.txt	9839	0644	edit dl rm
mimewriter.rst.txt	3360	0644	edit dl rm
mimify.rst.txt	3519	0644	edit dl rm
miniaeframe.rst.txt	2564	0644	edit dl rm
misc.rst.txt	248	0644	edit dl rm
mm.rst.txt	447	0644	edit dl rm
mmap.rst.txt	10481	0644	edit dl rm
modulefinder.rst.txt	3380	0644	edit dl rm
modules.rst.txt	382	0644	edit dl rm
msilib.rst.txt	19062	0644	edit dl rm
msvcrt.rst.txt	4346	0644	edit dl rm
multifile.rst.txt	6613	0644	edit dl rm
multiprocessing.rst.txt	92621	0644	edit dl rm
mutex.rst.txt	1939	0644	edit dl rm
netdata.rst.txt	432	0644	edit dl rm
netrc.rst.txt	3119	0644	edit dl rm
new.rst.txt	2653	0644	edit dl rm
nis.rst.txt	2108	0644	edit dl rm
nntplib.rst.txt	14531	0644	edit dl rm
numbers.rst.txt	8007	0644	edit dl rm
numeric.rst.txt	751	0644	edit dl rm
operator.rst.txt	22092	0644	edit dl rm
optparse.rst.txt	77101	0644	edit dl rm
os.path.rst.txt	13094	0644	edit dl rm
os.rst.txt	82580	0644	edit dl rm
ossaudiodev.rst.txt	17309	0644	edit dl rm
othergui.rst.txt	2721	0644	edit dl rm
parser.rst.txt	15385	0644	edit dl rm
pdb.rst.txt	16043	0644	edit dl rm
persistence.rst.txt	826	0644	edit dl rm
pickle.rst.txt	37262	0644	edit dl rm
pickletools.rst.txt	1997	0644	edit dl rm
pipes.rst.txt	3786	0644	edit dl rm
pkgutil.rst.txt	7714	0644	edit dl rm
platform.rst.txt	9554	0644	edit dl rm
plistlib.rst.txt	4134	0644	edit dl rm
popen2.rst.txt	7022	0644	edit dl rm
poplib.rst.txt	6220	0644	edit dl rm
posix.rst.txt	3630	0644	edit dl rm
posixfile.rst.txt	7200	0644	edit dl rm
pprint.rst.txt	9071	0644	edit dl rm
profile.rst.txt	28666	0644	edit dl rm
pty.rst.txt	1762	0644	edit dl rm
pwd.rst.txt	2725	0644	edit dl rm
pyclbr.rst.txt	3296	0644	edit dl rm
pydoc.rst.txt	4083	0644	edit dl rm
pyexpat.rst.txt	28891	0644	edit dl rm
python.rst.txt	514	0644	edit dl rm
py_compile.rst.txt	2479	0644	edit dl rm
queue.rst.txt	7034	0644	edit dl rm
quopri.rst.txt	2670	0644	edit dl rm
random.rst.txt	13319	0644	edit dl rm
re.rst.txt	55102	0644	edit dl rm
readline.rst.txt	10513	0644	edit dl rm
repr.rst.txt	4718	0644	edit dl rm
resource.rst.txt	9595	0644	edit dl rm
restricted.rst.txt	3327	0644	edit dl rm
rexec.rst.txt	11742	0644	edit dl rm
rfc822.rst.txt	14037	0644	edit dl rm
rlcompleter.rst.txt	2494	0644	edit dl rm
robotparser.rst.txt	2190	0644	edit dl rm
runpy.rst.txt	6938	0644	edit dl rm
sched.rst.txt	4644	0644	edit dl rm
scrolledtext.rst.txt	1379	0644	edit dl rm
select.rst.txt	20705	0644	edit dl rm
sets.rst.txt	14973	0644	edit dl rm
sgi.rst.txt	322	0644	edit dl rm
sgmllib.rst.txt	10664	0644	edit dl rm
sha.rst.txt	2807	0644	edit dl rm
shelve.rst.txt	8319	0644	edit dl rm
shlex.rst.txt	11313	0644	edit dl rm
shutil.rst.txt	13491	0644	edit dl rm
signal.rst.txt	10719	0644	edit dl rm
simplehttpserver.rst.txt	4559	0644	edit dl rm
simplexmlrpcserver.rst.txt	10881	0644	edit dl rm
site.rst.txt	7880	0644	edit dl rm
smtpd.rst.txt	2464	0644	edit dl rm
smtplib.rst.txt	14906	0644	edit dl rm
sndhdr.rst.txt	1759	0644	edit dl rm
socket.rst.txt	40765	0644	edit dl rm
socketserver.rst.txt	22512	0644	edit dl rm
someos.rst.txt	599	0644	edit dl rm
spwd.rst.txt	2825	0644	edit dl rm
sqlite3.rst.txt	35448	0644	edit dl rm
ssl.rst.txt	76554	0644	edit dl rm
stat.rst.txt	7778	0644	edit dl rm
statvfs.rst.txt	1300	0644	edit dl rm
stdtypes.rst.txt	122668	0644	edit dl rm
string.rst.txt	44085	0644	edit dl rm
stringio.rst.txt	4166	0644	edit dl rm
stringprep.rst.txt	4238	0644	edit dl rm
strings.rst.txt	746	0644	edit dl rm
struct.rst.txt	17100	0644	edit dl rm
subprocess.rst.txt	33648	0644	edit dl rm
sun.rst.txt	249	0644	edit dl rm
sunau.rst.txt	7124	0644	edit dl rm
sunaudio.rst.txt	5849	0644	edit dl rm
symbol.rst.txt	975	0644	edit dl rm
symtable.rst.txt	5064	0644	edit dl rm
sys.rst.txt	47520	0644	edit dl rm
sysconfig.rst.txt	7639	0644	edit dl rm
syslog.rst.txt	3931	0644	edit dl rm
tabnanny.rst.txt	1999	0644	edit dl rm
tarfile.rst.txt	28214	0644	edit dl rm
telnetlib.rst.txt	7482	0644	edit dl rm
tempfile.rst.txt	10504	0644	edit dl rm
termios.rst.txt	3733	0644	edit dl rm
test.rst.txt	17659	0644	edit dl rm
textwrap.rst.txt	8552	0644	edit dl rm
thread.rst.txt	6588	0644	edit dl rm
threading.rst.txt	32468	0644	edit dl rm
time.rst.txt	26020	0644	edit dl rm
timeit.rst.txt	11598	0644	edit dl rm
tix.rst.txt	22693	0644	edit dl rm
tk.rst.txt	1612	0644	edit dl rm
tkinter.rst.txt	33456	0644	edit dl rm
token.rst.txt	2451	0644	edit dl rm
tokenize.rst.txt	5570	0644	edit dl rm
trace.rst.txt	6724	0644	edit dl rm
traceback.rst.txt	10711	0644	edit dl rm
ttk.rst.txt	57411	0644	edit dl rm
tty.rst.txt	1011	0644	edit dl rm
turtle.rst.txt	64097	0644	edit dl rm
types.rst.txt	6200	0644	edit dl rm
undoc.rst.txt	6550	0644	edit dl rm
unicodedata.rst.txt	5736	0644	edit dl rm
unittest.rst.txt	82952	0644	edit dl rm
unix.rst.txt	490	0644	edit dl rm
urllib.rst.txt	24960	0644	edit dl rm
urllib2.rst.txt	35211	0644	edit dl rm
urlparse.rst.txt	16071	0644	edit dl rm
user.rst.txt	2748	0644	edit dl rm
userdict.rst.txt	9290	0644	edit dl rm
uu.rst.txt	2369	0644	edit dl rm
uuid.rst.txt	8378	0644	edit dl rm
warnings.rst.txt	19815	0644	edit dl rm
wave.rst.txt	5047	0644	edit dl rm
weakref.rst.txt	12926	0644	edit dl rm
webbrowser.rst.txt	9863	0644	edit dl rm
whichdb.rst.txt	931	0644	edit dl rm
windows.rst.txt	273	0644	edit dl rm
winsound.rst.txt	5066	0644	edit dl rm
wsgiref.rst.txt	30567	0644	edit dl rm
xdrlib.rst.txt	8077	0644	edit dl rm
xml.dom.minidom.rst.txt	11208	0644	edit dl rm
xml.dom.pulldom.rst.txt	1571	0644	edit dl rm
xml.dom.rst.txt	40182	0644	edit dl rm
xml.etree.elementtree.rst.txt	35707	0644	edit dl rm
xml.rst.txt	6090	0644	edit dl rm
xml.sax.handler.rst.txt	15371	0644	edit dl rm
xml.sax.reader.rst.txt	12257	0644	edit dl rm
xml.sax.rst.txt	6460	0644	edit dl rm
xml.sax.utils.rst.txt	3560	0644	edit dl rm
xmlrpclib.rst.txt	22559	0644	edit dl rm
zipfile.rst.txt	18871	0644	edit dl rm
zipimport.rst.txt	5957	0644	edit dl rm
zlib.rst.txt	12766	0644	edit dl rm
_winreg.rst.txt	23305	0644	edit dl rm
__builtin__.rst.txt	1494	0644	edit dl rm
__future__.rst.txt	4952	0644	edit dl rm
__main__.rst.txt	535	0644	edit dl rm

Edit: /usr/share/doc/python2-docs/html/_sources/library/csv.rst.txt (22757B)

:mod:`csv` --- CSV File Reading and Writing
===========================================

.. module:: csv
   :synopsis: Write and read tabular data to and from delimited files.
.. sectionauthor:: Skip Montanaro <skip@pobox.com>

.. versionadded:: 2.3

.. index::
   single: csv
   pair: data; tabular

The so-called CSV (Comma Separated Values) format is the most common import and
export format for spreadsheets and databases.  There is no "CSV standard", so
the format is operationally defined by the many applications which read and
write it.  The lack of a standard means that subtle differences often exist in
the data produced and consumed by different applications.  These differences can
make it annoying to process CSV files from multiple sources.  Still, while the
delimiters and quoting characters vary, the overall format is similar enough
that it is possible to write a single module which can efficiently manipulate
such data, hiding the details of reading and writing the data from the
programmer.

The :mod:`csv` module implements classes to read and write tabular data in CSV
format.  It allows programmers to say, "write this data in the format preferred
by Excel," or "read data from this file which was generated by Excel," without
knowing the precise details of the CSV format used by Excel.  Programmers can
also describe the CSV formats understood by other applications or define their
own special-purpose CSV formats.

The :mod:`csv` module's :class:`reader` and :class:`writer` objects read and
write sequences.  Programmers can also read and write data in dictionary form
using the :class:`DictReader` and :class:`DictWriter` classes.

.. note::

This version of the :mod:`csv` module doesn't support Unicode input.  Also,
   there are currently some issues regarding ASCII NUL characters.  Accordingly,
   all input should be UTF-8 or printable ASCII to be safe; see the examples in
   section :ref:`csv-examples`.

.. seealso::

:pep:`305` - CSV File API
      The Python Enhancement Proposal which proposed this addition to Python.

.. _csv-contents:

Module Contents
---------------

The :mod:`csv` module defines the following functions:

.. function:: reader(csvfile, dialect='excel', **fmtparams)

Return a reader object which will iterate over lines in the given *csvfile*.
   *csvfile* can be any object which supports the :term:`iterator` protocol and returns a
   string each time its :meth:`!next` method is called --- file objects and list
   objects are both suitable.   If *csvfile* is a file object, it must be opened
   with the 'b' flag on platforms where that makes a difference.  An optional
   *dialect* parameter can be given which is used to define a set of parameters
   specific to a particular CSV dialect.  It may be an instance of a subclass of
   the :class:`Dialect` class or one of the strings returned by the
   :func:`list_dialects` function.  The other optional *fmtparams* keyword arguments
   can be given to override individual formatting parameters in the current
   dialect.  For full details about the dialect and formatting parameters, see
   section :ref:`csv-fmt-params`.

Each row read from the csv file is returned as a list of strings.  No
   automatic data type conversion is performed.

A short usage example::

>>> import csv
      >>> with open('eggs.csv', 'rb') as csvfile:
      ...     spamreader = csv.reader(csvfile, delimiter=' ', quotechar='|')
      ...     for row in spamreader:
      ...         print ', '.join(row)
      Spam, Spam, Spam, Spam, Spam, Baked Beans
      Spam, Lovely Spam, Wonderful Spam

.. versionchanged:: 2.5
      The parser is now stricter with respect to multi-line quoted fields. Previously,
      if a line ended within a quoted field without a terminating newline character, a
      newline would be inserted into the returned field. This behavior caused problems
      when reading files which contained carriage return characters within fields.
      The behavior was changed to return the field without inserting newlines. As a
      consequence, if newlines embedded within fields are important, the input should
      be split into lines in a manner which preserves the newline characters.

.. function:: writer(csvfile, dialect='excel', **fmtparams)

Return a writer object responsible for converting the user's data into delimited
   strings on the given file-like object.  *csvfile* can be any object with a
   :func:`write` method.  If *csvfile* is a file object, it must be opened with the
   'b' flag on platforms where that makes a difference.  An optional *dialect*
   parameter can be given which is used to define a set of parameters specific to a
   particular CSV dialect.  It may be an instance of a subclass of the
   :class:`Dialect` class or one of the strings returned by the
   :func:`list_dialects` function.  The other optional *fmtparams* keyword arguments
   can be given to override individual formatting parameters in the current
   dialect.  For full details about the dialect and formatting parameters, see
   section :ref:`csv-fmt-params`. To make it
   as easy as possible to interface with modules which implement the DB API, the
   value :const:`None` is written as the empty string.  While this isn't a
   reversible transformation, it makes it easier to dump SQL NULL data values to
   CSV files without preprocessing the data returned from a ``cursor.fetch*`` call.
   Floats are stringified with :func:`repr` before being written.
   All other non-string data are stringified with :func:`str` before being written.

A short usage example::

import csv
      with open('eggs.csv', 'wb') as csvfile:
          spamwriter = csv.writer(csvfile, delimiter=' ',
                                  quotechar='|', quoting=csv.QUOTE_MINIMAL)
          spamwriter.writerow(['Spam'] * 5 + ['Baked Beans'])
          spamwriter.writerow(['Spam', 'Lovely Spam', 'Wonderful Spam'])

.. function:: register_dialect(name[, dialect], **fmtparams)

Associate *dialect* with *name*.  *name* must be a string or Unicode object. The
   dialect can be specified either by passing a sub-class of :class:`Dialect`, or
   by *fmtparams* keyword arguments, or both, with keyword arguments overriding
   parameters of the dialect. For full details about the dialect and formatting
   parameters, see section :ref:`csv-fmt-params`.

.. function:: unregister_dialect(name)

Delete the dialect associated with *name* from the dialect registry.  An
   :exc:`Error` is raised if *name* is not a registered dialect name.

.. function:: get_dialect(name)

Return the dialect associated with *name*.  An :exc:`Error` is raised if *name*
   is not a registered dialect name.

.. versionchanged:: 2.5
      This function now returns an immutable :class:`Dialect`.  Previously an
      instance of the requested dialect was returned.  Users could modify the
      underlying class, changing the behavior of active readers and writers.

.. function:: list_dialects()

Return the names of all registered dialects.

.. function:: field_size_limit([new_limit])

Returns the current maximum field size allowed by the parser. If *new_limit* is
   given, this becomes the new limit.

.. versionadded:: 2.5

The :mod:`csv` module defines the following classes:

.. class:: DictReader(f, fieldnames=None, restkey=None, restval=None, \
                      dialect='excel', *args, **kwds)

Create an object which operates like a regular reader but maps the
   information read into a dict whose keys are given by the optional
   *fieldnames* parameter.  The *fieldnames* parameter is a :ref:`sequence
   <collections-abstract-base-classes>` whose elements are associated with the
   fields of the input data in order. These elements become the keys of the
   resulting dictionary.  If the *fieldnames* parameter is omitted, the values
   in the first row of the file *f* will be used as the fieldnames.  If the
   row read has more fields than the fieldnames sequence, the remaining data is
   added as a sequence keyed by the value of *restkey*.  If the row read has
   fewer fields than the fieldnames sequence, the remaining keys take the value
   of the optional *restval* parameter.  Any other optional or keyword
   arguments are passed to the underlying :class:`reader` instance.

A short usage example::

>>> import csv
       >>> with open('names.csv') as csvfile:
       ...     reader = csv.DictReader(csvfile)
       ...     for row in reader:
       ...         print(row['first_name'], row['last_name'])
       ...
       Baked Beans
       Lovely Spam
       Wonderful Spam

.. class:: DictWriter(f, fieldnames, restval='', extrasaction='raise', \
                      dialect='excel', *args, **kwds)

Create an object which operates like a regular writer but maps dictionaries
   onto output rows.  The *fieldnames* parameter is a :ref:`sequence
   <collections-abstract-base-classes>` of keys that identify the order in
   which values in the dictionary passed to the :meth:`writerow` method are
   written to the file *f*.  The optional *restval* parameter specifies the
   value to be written if the dictionary is missing a key in *fieldnames*.  If
   the dictionary passed to the :meth:`writerow` method contains a key not
   found in *fieldnames*, the optional *extrasaction* parameter indicates what
   action to take.  If it is set to ``'raise'`` a :exc:`ValueError` is raised.
   If it is set to ``'ignore'``, extra values in the dictionary are ignored.
   Any other optional or keyword arguments are passed to the underlying
   :class:`writer` instance.

Note that unlike the :class:`DictReader` class, the *fieldnames* parameter
   of the :class:`DictWriter` is not optional.  Since Python's :class:`dict`
   objects are not ordered, there is not enough information available to deduce
   the order in which the row should be written to the file *f*.

A short usage example::

import csv

with open('names.csv', 'w') as csvfile:
           fieldnames = ['first_name', 'last_name']
           writer = csv.DictWriter(csvfile, fieldnames=fieldnames)

writer.writeheader()
           writer.writerow({'first_name': 'Baked', 'last_name': 'Beans'})
           writer.writerow({'first_name': 'Lovely', 'last_name': 'Spam'})
           writer.writerow({'first_name': 'Wonderful', 'last_name': 'Spam'})

.. class:: Dialect

The :class:`Dialect` class is a container class relied on primarily for its
   attributes, which are used to define the parameters for a specific
   :class:`reader` or :class:`writer` instance.

.. class:: excel()

The :class:`excel` class defines the usual properties of an Excel-generated CSV
   file.  It is registered with the dialect name ``'excel'``.

.. class:: excel_tab()

The :class:`excel_tab` class defines the usual properties of an Excel-generated
   TAB-delimited file.  It is registered with the dialect name ``'excel-tab'``.

.. class:: Sniffer()

The :class:`Sniffer` class is used to deduce the format of a CSV file.

The :class:`Sniffer` class provides two methods:

.. method:: sniff(sample, delimiters=None)

Analyze the given *sample* and return a :class:`Dialect` subclass
      reflecting the parameters found.  If the optional *delimiters* parameter
      is given, it is interpreted as a string containing possible valid
      delimiter characters.

.. method:: has_header(sample)

Analyze the sample text (presumed to be in CSV format) and return
      :const:`True` if the first row appears to be a series of column headers.

An example for :class:`Sniffer` use::

with open('example.csv', 'rb') as csvfile:
       dialect = csv.Sniffer().sniff(csvfile.read(1024))
       csvfile.seek(0)
       reader = csv.reader(csvfile, dialect)
       # ... process CSV file contents here ...

The :mod:`csv` module defines the following constants:

.. data:: QUOTE_ALL

Instructs :class:`writer` objects to quote all fields.

.. data:: QUOTE_MINIMAL

Instructs :class:`writer` objects to only quote those fields which contain
   special characters such as *delimiter*, *quotechar* or any of the characters in
   *lineterminator*.

.. data:: QUOTE_NONNUMERIC

Instructs :class:`writer` objects to quote all non-numeric fields.

Instructs the reader to convert all non-quoted fields to type *float*.

.. data:: QUOTE_NONE

Instructs :class:`writer` objects to never quote fields.  When the current
   *delimiter* occurs in output data it is preceded by the current *escapechar*
   character.  If *escapechar* is not set, the writer will raise :exc:`Error` if
   any characters that require escaping are encountered.

Instructs :class:`reader` to perform no special processing of quote characters.

The :mod:`csv` module defines the following exception:

.. exception:: Error

Raised by any of the functions when an error is detected.

.. _csv-fmt-params:

Dialects and Formatting Parameters
----------------------------------

To make it easier to specify the format of input and output records, specific
formatting parameters are grouped together into dialects.  A dialect is a
subclass of the :class:`Dialect` class having a set of specific methods and a
single :meth:`validate` method.  When creating :class:`reader` or
:class:`writer` objects, the programmer can specify a string or a subclass of
the :class:`Dialect` class as the dialect parameter.  In addition to, or instead
of, the *dialect* parameter, the programmer can also specify individual
formatting parameters, which have the same names as the attributes defined below
for the :class:`Dialect` class.

Dialects support the following attributes:

.. attribute:: Dialect.delimiter

A one-character string used to separate fields.  It defaults to ``','``.

.. attribute:: Dialect.doublequote

Controls how instances of *quotechar* appearing inside a field should
   themselves be quoted.  When :const:`True`, the character is doubled. When
   :const:`False`, the *escapechar* is used as a prefix to the *quotechar*.  It
   defaults to :const:`True`.

On output, if *doublequote* is :const:`False` and no *escapechar* is set,
   :exc:`Error` is raised if a *quotechar* is found in a field.

.. attribute:: Dialect.escapechar

A one-character string used by the writer to escape the *delimiter* if *quoting*
   is set to :const:`QUOTE_NONE` and the *quotechar* if *doublequote* is
   :const:`False`. On reading, the *escapechar* removes any special meaning from
   the following character. It defaults to :const:`None`, which disables escaping.

.. attribute:: Dialect.lineterminator

The string used to terminate lines produced by the :class:`writer`. It defaults
   to ``'\r\n'``.

.. note::

The :class:`reader` is hard-coded to recognise either ``'\r'`` or ``'\n'`` as
      end-of-line, and ignores *lineterminator*. This behavior may change in the
      future.

.. attribute:: Dialect.quotechar

A one-character string used to quote fields containing special characters, such
   as the *delimiter* or *quotechar*, or which contain new-line characters.  It
   defaults to ``'"'``.

.. attribute:: Dialect.quoting

Controls when quotes should be generated by the writer and recognised by the
   reader.  It can take on any of the :const:`QUOTE_\*` constants (see section
   :ref:`csv-contents`) and defaults to :const:`QUOTE_MINIMAL`.

.. attribute:: Dialect.skipinitialspace

When :const:`True`, whitespace immediately following the *delimiter* is ignored.
   The default is :const:`False`.

.. attribute:: Dialect.strict

When ``True``, raise exception :exc:`Error` on bad CSV input.
   The default is ``False``.

Reader Objects
--------------

Reader objects (:class:`DictReader` instances and objects returned by the
:func:`reader` function) have the following public methods:

.. method:: csvreader.next()

Return the next row of the reader's iterable object as a list, parsed according
   to the current dialect.

Reader objects have the following public attributes:

.. attribute:: csvreader.dialect

A read-only description of the dialect in use by the parser.

.. attribute:: csvreader.line_num

The number of lines read from the source iterator. This is not the same as the
   number of records returned, as records can span multiple lines.

.. versionadded:: 2.5

DictReader objects have the following public attribute:

.. attribute:: csvreader.fieldnames

If not passed as a parameter when creating the object, this attribute is
   initialized upon first access or when the first record is read from the
   file.

.. versionchanged:: 2.6

Writer Objects
--------------

:class:`Writer` objects (:class:`DictWriter` instances and objects returned by
the :func:`writer` function) have the following public methods.  A *row* must be
a sequence of strings or numbers for :class:`Writer` objects and a dictionary
mapping fieldnames to strings or numbers (by passing them through :func:`str`
first) for :class:`DictWriter` objects.  Note that complex numbers are written
out surrounded by parens. This may cause some problems for other programs which
read CSV files (assuming they support complex numbers at all).

.. method:: csvwriter.writerow(row)

Write the *row* parameter to the writer's file object, formatted according to
   the current dialect.

.. method:: csvwriter.writerows(rows)

Write all elements in *rows* (an iterable of *row* objects as described
   above) to the writer's file object, formatted according to the current
   dialect.

Writer objects have the following public attribute:

.. attribute:: csvwriter.dialect

A read-only description of the dialect in use by the writer.

DictWriter objects have the following public method:

.. method:: DictWriter.writeheader()

Write a row with the field names (as specified in the constructor).

.. versionadded:: 2.7

.. _csv-examples:

Examples
--------

The simplest example of reading a CSV file::

import csv
   with open('some.csv', 'rb') as f:
       reader = csv.reader(f)
       for row in reader:
           print row

Reading a file with an alternate format::

import csv
   with open('passwd', 'rb') as f:
       reader = csv.reader(f, delimiter=':', quoting=csv.QUOTE_NONE)
       for row in reader:
           print row

The corresponding simplest possible writing example is::

import csv
   with open('some.csv', 'wb') as f:
       writer = csv.writer(f)
       writer.writerows(someiterable)

Registering a new dialect::

import csv
   csv.register_dialect('unixpwd', delimiter=':', quoting=csv.QUOTE_NONE)
   with open('passwd', 'rb') as f:
       reader = csv.reader(f, 'unixpwd')

A slightly more advanced use of the reader --- catching and reporting errors::

import csv, sys
   filename = 'some.csv'
   with open(filename, 'rb') as f:
       reader = csv.reader(f)
       try:
           for row in reader:
               print row
       except csv.Error as e:
           sys.exit('file %s, line %d: %s' % (filename, reader.line_num, e))

And while the module doesn't directly support parsing strings, it can easily be
done::

import csv
   for row in csv.reader(['one,two,three']):
       print row

The :mod:`csv` module doesn't directly support reading and writing Unicode, but
it is 8-bit-clean save for some problems with ASCII NUL characters.  So you can
write functions or classes that handle the encoding and decoding for you as long
as you avoid encodings like UTF-16 that use NULs.  UTF-8 is recommended.

:func:`unicode_csv_reader` below is a :term:`generator` that wraps :class:`csv.reader`
to handle Unicode CSV data (a list of Unicode strings).  :func:`utf_8_encoder`
is a :term:`generator` that encodes the Unicode strings as UTF-8, one string (or row) at
a time.  The encoded strings are parsed by the CSV reader, and
:func:`unicode_csv_reader` decodes the UTF-8-encoded cells back into Unicode::

import csv

def unicode_csv_reader(unicode_csv_data, dialect=csv.excel, **kwargs):
       # csv.py doesn't do Unicode; encode temporarily as UTF-8:
       csv_reader = csv.reader(utf_8_encoder(unicode_csv_data),
                               dialect=dialect, **kwargs)
       for row in csv_reader:
           # decode UTF-8 back to Unicode, cell by cell:
           yield [unicode(cell, 'utf-8') for cell in row]

def utf_8_encoder(unicode_csv_data):
       for line in unicode_csv_data:
           yield line.encode('utf-8')

For all other encodings the following :class:`UnicodeReader` and
:class:`UnicodeWriter` classes can be used. They take an additional *encoding*
parameter in their constructor and make sure that the data passes the real
reader or writer encoded as UTF-8::

import csv, codecs, cStringIO

class UTF8Recoder:
       """
       Iterator that reads an encoded stream and reencodes the input to UTF-8
       """
       def __init__(self, f, encoding):
           self.reader = codecs.getreader(encoding)(f)

def __iter__(self):
           return self

def next(self):
           return self.reader.next().encode("utf-8")

class UnicodeReader:
       """
       A CSV reader which will iterate over lines in the CSV file "f",
       which is encoded in the given encoding.
       """

def __init__(self, f, dialect=csv.excel, encoding="utf-8", **kwds):
           f = UTF8Recoder(f, encoding)
           self.reader = csv.reader(f, dialect=dialect, **kwds)

def next(self):
           row = self.reader.next()
           return [unicode(s, "utf-8") for s in row]

def __iter__(self):
           return self

class UnicodeWriter:
       """
       A CSV writer which will write rows to CSV file "f",
       which is encoded in the given encoding.
       """

def __init__(self, f, dialect=csv.excel, encoding="utf-8", **kwds):
           # Redirect output to a queue
           self.queue = cStringIO.StringIO()
           self.writer = csv.writer(self.queue, dialect=dialect, **kwds)
           self.stream = f
           self.encoder = codecs.getincrementalencoder(encoding)()

def writerow(self, row):
           self.writer.writerow([s.encode("utf-8") for s in row])
           # Fetch UTF-8 output from the queue ...
           data = self.queue.getvalue()
           data = data.decode("utf-8")
           # ... and reencode it into the target encoding
           data = self.encoder.encode(data)
           # write to the target stream
           self.stream.write(data)
           # empty queue
           self.queue.truncate(0)

def writerows(self, rows):
           for row in rows:
               self.writerow(row)

cmd: