Description

assignee = None
closed_at = None
created_at = <Date 2019-12-18.20:50:42.912>
labels = ['type-bug', 'library', '3.9']
title = "Csv sniffer doesn't attempt to determine and set escape character."
updated_at = <Date 2019-12-18.20:50:42.912>
user = 'https://github.com/evanw2'

activity = <Date 2019-12-18.20:50:42.912>
actor = 'evan.whitfield'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-12-18.20:50:42.912>
creator = 'evan.whitfield'
dependencies = []
files = []
hgrepos = []
issue_num = 39092
keywords = []
message_count = 1.0
messages = ['358645']
nosy_count = 1.0
nosy_names = ['evan.whitfield']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue39092'
versions = ['Python 3.9']

Activity

1. evanw2 commented on Dec 18, 2019

   

   evanw2mannequin

   on Dec 18, 2019

   MannequinAuthor

   More actions

   I observed a false positive for the csv sniffer has_header method. (It thought there was a header when there was not.) This is due to the fact that in has_header, it determines the csv dialect by sniffing it, and failed to determine that the file I was using had an escape character of '\'. Since it doesn't set the escape character, it then incorrectly broke the first line of the file into columns, since it encountered an escaped quote within a quoted column, and treated that as the end of that column. (It correctly determined that the dialect wasn't doublequote, but apparently still needs to have the escape character set to handle an escaped quotechar.)

   I think one (or both) of these things should be done here to avoid this false positive:
   1.) Allow a dialect to be passed to has_header, so that someone could specify the escape character of the dialect if it were known.
   2.) Allow the sniff method of the Sniffer class to detect and set the escapechar.
2. evanw2

   added

   3.9 (EOL)end of lifeend of life

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Dec 18, 2019
3. ezio-melotti

   transferred this issue fromon Apr 10, 2022
4. serhiy-storchaka

   added this to CSV issues 📊on May 19, 2022
5. serhiy-storchaka

   self-assigned this

   on Jan 9, 2024
6. serhiy-storchaka

   added a commit that references this issue on Jul 21, 2026

   gh-83273: Rewrite csv.Sniffer dialect detection using trial parsing (G…

   25fea6d
7. serhiy-storchaka

   closed this as completedin #153694on Jul 21, 2026
8. github-project-automation

   moved this to Done in CSV issues 📊on Jul 21, 2026
9. serhiy-storchaka

   added

   3.16new features, bugs and security fixesnew features, bugs and security fixes

   and removed

   3.9 (EOL)end of lifeend of life

   on Jul 21, 2026

Issue actions