[New-bugs-announce] [issue39964] adding a string to a list works differently with x+='' compared to x=x+''

[Richard King]

New submission from Richard King <rickbking at comcast.net>:

x = ['a']

x += ' ' results in ['a',' ']

x = x + ' ' results in an exception:
Traceback (most recent call last):
  File "<input>", line 1, in <module>
TypeError: can only concatenate list (not "str") to list

It behaves the same in 2.7.15 and 3.7.2.

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components: Windows
messages: 364213
nosy: paul.moore, rickbking, steve.dower, tim.golden, zach.ware
priority: normal
severity: normal
status: open
title: adding a string to a list works differently with x+='' compared to x=x+''
type: behavior
versions: Python 2.7, Python 3.7

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue39964>
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