Why can I assign True = False (Python 2.7.9)

Question

Why am I able to assign the Python keyword True to equal the Python keyword False using Python 2.7.9?

Python 2.7.9 (v2.7.9:648dcafa7e5f, Dec 10 2014, 10:10:46)
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
>>> True
True
>>> True = False
>>> True
False
>>>

But when switching over to Python 3.4.3:

Python 3.4.3 (v3.4.3:9b73f1c3e601, Feb 23 2015, 02:52:03)
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
>>> True = False
  File "<stdin>", line 1
SyntaxError: can't assign to keyword
>>>

Did you try Googling something like "python true false assign to keyword"? — TigerhawkT3, Jun 30 '15 at 19:08
This is the same thing as assigning `max` to `100` or `input` to `'Hello'`. — Malik Brahimi, Jun 30 '15 at 19:09
Am I the only one who read this question and immediately thought "I guess they changed it to a keyword, cool"? All the answers basically just repeat the question and add "yes, this occurs." — TigerhawkT3, Jun 30 '15 at 19:21

score 9 · Accepted Answer · answered Jun 30 '15 at 19:07

9

True and False were builtins in Python 2, but in Python 3 they are keywords — thus the error message. Strictly speaking, you're not assigning to them but shadowing them — which you can't do with a keyword.

answered Jun 30 '15 at 19:07

JasonFruit

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score 2 · Answer 2 · answered Jun 30 '15 at 19:07

2

In python 3.x, True and False are reserved words

answered Jun 30 '15 at 19:07

James

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2

They know that, they pointed that out in their 2nd example. Re-read the question. – Cory Kramer Jun 30 '15 at 19:07
1

@CoryKramer, Sorry if my answer wasn't clear. You can do this in python 2.x because True and False are not [reserved words](https://docs.python.org/2.5/ref/keywords.html). – James Jun 30 '15 at 19:09

score 2 · Answer 3 · answered Jun 30 '15 at 19:07

2

Because in Python 3.X it's a keyword, and in 2.7.X it's a variable (as True=4869 works too, as well as False=[4,8,6,9])

answered Jun 30 '15 at 19:07

ForceBru

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Why can I assign True = False (Python 2.7.9)

3 Answers3