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authorRaymond Hettinger <python@rcn.com>2016-08-30 19:35:50 (GMT)
committerRaymond Hettinger <python@rcn.com>2016-08-30 19:35:50 (GMT)
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Issue #27842: The csv.DictReader now returns rows of type OrderedDict.
Diffstat (limited to 'Doc/library/csv.rst')
-rw-r--r--Doc/library/csv.rst39
1 files changed, 24 insertions, 15 deletions
diff --git a/Doc/library/csv.rst b/Doc/library/csv.rst
index 7fb4fc8..6341bc3 100644
--- a/Doc/library/csv.rst
+++ b/Doc/library/csv.rst
@@ -149,18 +149,25 @@ The :mod:`csv` module defines the following classes:
.. class:: DictReader(csvfile, 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 :mod:`sequence
- <collections.abc>` 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 *csvfile* 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.
+ Create an object that operates like a regular reader but maps the
+ information in each row to an :mod:`OrderedDict <collections.OrderedDict>`
+ whose keys are given by the optional *fieldnames* parameter.
+
+ The *fieldnames* parameter is a :term:`sequence`. If *fieldnames* is
+ omitted, the values in the first row of the *csvfile* will be used as the
+ fieldnames. Regardless of how the fieldnames are determined, the ordered
+ dictionary preserves their original ordering.
+
+ If a row has more fields than fieldnames, the remaining data is put in a
+ list and stored with the fieldname specified by *restkey* (which defaults
+ to ``None``). If a non-blank row has fewer fields than fieldnames, the
+ missing values are filled-in with ``None``.
+
+ All other optional or keyword arguments are passed to the underlying
+ :class:`reader` instance.
+
+ .. versionchanged:: 3.6
+ Returned rows are now of type :class:`OrderedDict`.
A short usage example::
@@ -170,9 +177,11 @@ The :mod:`csv` module defines the following classes:
... for row in reader:
... print(row['first_name'], row['last_name'])
...
- Baked Beans
- Lovely Spam
- Wonderful Spam
+ Eric Idle
+ John Cleese
+
+ >>> print(row)
+ OrderedDict([('first_name', 'John'), ('last_name', 'Cleese')])
.. class:: DictWriter(csvfile, fieldnames, restval='', extrasaction='raise', \