Trailing backslash in raw string format causes EOL

[cfgbd]

BPO	27947
Nosy	@ammaraskar

^{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 2016-09-03.03:05:31.355>
created_at = <Date 2016-09-03.02:47:54.846>
labels = ['type-bug', 'invalid']
title = 'Trailing backslash in raw string format causes EOL'
updated_at = <Date 2016-09-03.03:12:11.477>
user = 'https://bugs.python.org/cfgbd'

bugs.python.org fields:

activity = <Date 2016-09-03.03:12:11.477>
actor = 'cfgbd'
assignee = 'none'
closed = True
closed_date = <Date 2016-09-03.03:05:31.355>
closer = 'tim.peters'
components = []
creation = <Date 2016-09-03.02:47:54.846>
creator = 'cfgbd'
dependencies = []
files = []
hgrepos = []
issue_num = 27947
keywords = []
message_count = 3.0
messages = ['274282', '274283', '274284']
nosy_count = 2.0
nosy_names = ['ammar2', 'cfgbd']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue27947'
versions = ['Python 3.2']

[cfgbd]

In python shell, I typed words and got result as follows. It seems that the use of 'r' before a literal string may cause an error that the an odd '\' at the end of literal string blocked the quote.

>>> rb'abc\\\'
SyntaxError: EOL while scanning string literal
>>> rb'abc\\'
b'abc\\\\'
>>> br'abc\\\ '
b'abc\\\\\\ '
>>> br'abc\\\'
SyntaxError: EOL while scanning string literal
>>> r'\\'
'\\\\'
>>> r'\\\'
SyntaxError: EOL while scanning string literal

[ammaraskar]

This isn't a bug, in fact this very behavior is documented within the string docs, please read the last paragraph here:

https://docs.python.org/3/reference/lexical_analysis.html#string-and-bytes-literals

[cfgbd]

Thanks for comment. Here I got my answer from string docs.

Even in a raw literal, quotes can be escaped with a backslash, but the backslash remains in the result; for example, r"\"" is a valid string literal consisting of two characters: a backslash and a double quote; r"\" is not a valid string literal (even a raw string cannot end in an odd number of backslashes). Specifically, a raw literal cannot end in a single backslash (since the backslash would escape the following quote character). Note also that a single backslash followed by a newline is interpreted as those two characters as part of the literal, not as a line continuation.