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csv.reader accepts string instead of file object (duck typing gone bad) #46953

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roysmith mannequin opened this issue Apr 27, 2008 · 3 comments
Closed

csv.reader accepts string instead of file object (duck typing gone bad) #46953

roysmith mannequin opened this issue Apr 27, 2008 · 3 comments
Labels
stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error

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@roysmith
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Mannequin

roysmith mannequin commented Apr 27, 2008

BPO 2701
Nosy @smontanaro, @facundobatista

Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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GitHub fields:

assignee = None
closed_at = <Date 2008-06-21.15:48:58.320>
created_at = <Date 2008-04-27.02:59:50.468>
labels = ['invalid', 'type-bug', 'library']
title = 'csv.reader accepts string instead of file object (duck typing gone bad)'
updated_at = <Date 2008-06-21.15:48:58.269>
user = 'https://bugs.python.org/roysmith'

bugs.python.org fields:

activity = <Date 2008-06-21.15:48:58.269>
actor = 'facundobatista'
assignee = 'none'
closed = True
closed_date = <Date 2008-06-21.15:48:58.320>
closer = 'facundobatista'
components = ['Library (Lib)']
creation = <Date 2008-04-27.02:59:50.468>
creator = 'roysmith'
dependencies = []
files = []
hgrepos = []
issue_num = 2701
keywords = []
message_count = 3.0
messages = ['65871', '65884', '68502']
nosy_count = 3.0
nosy_names = ['skip.montanaro', 'facundobatista', 'roysmith']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue2701'
versions = ['Python 2.5']
@roysmith
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roysmith mannequin commented Apr 27, 2008

If you pass csv.reader() a filename as its first argument:

  csv.reader('filename')

instead of a file object like you're supposed to, you don't get an error.
You instead get a reader object which returns the characters which make up
the filename.

Technically, this is not a bug, since the documentation says, "csvfile can
be any object which supports the iterator protocol and returns a string
each time its next method is called", and a string meets that definition.
Still, this is unexpected behavior, and is almost certainly not what the
user intended. It would be useful if a way could be devised to catch this
kind of mistake.

@roysmith roysmith mannequin added stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error labels Apr 27, 2008
@smontanaro
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It's not a mistake. In fact, the csv unit tests make use of being able
to iterate over strings. I don't think this feature is going away.

@facundobatista
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Skip is right, this is working ok.

@ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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