[issue43833] Unexpected Parsing of Numeric Literals Concatenated with Boolean Operators

[sco1]

New submission from sco1 :

Came across this riddle today:

>>> [0x_for x in (1, 2, 3)]
[15]

Initially I thought this was related to PEP 515 but the unexpected behavior 
extends to simpler examples as well, such as:

>>> x = 5
>>> 123or x
123
>>> 123and x
5

I'm not familiar enough with C to understand why this is being parsed/tokenized 
this way, but this seems like it should instead be a SyntaxError. This appears 
to be fairly old behavior, as the non-underscored version works back to at 
least 2.7.

And a bonus:

>>> 0x1decade or more
31378142

--
messages: 390981
nosy: sco1
priority: normal
severity: normal
status: open
title: Unexpected Parsing of Numeric Literals Concatenated with Boolean 
Operators
type: behavior
versions: Python 3.10, Python 3.7, Python 3.8, Python 3.9

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[issue43833] Unexpected Parsing of Numeric Literals Concatenated with Boolean Operators

[sco1]

sco1  added the comment:

Sorry, the bonus, while fun, I don't think is related

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[issue43833] Unexpected Parsing of Numeric Literals Concatenated with Boolean Operators

[sco1]

sco1  added the comment:

Appreciate the additional historical context, I also was pointed to this in the 
documentation: 
https://docs.python.org/3/reference/lexical_analysis.html#whitespace-between-tokens

If a parsing change is undesired from a backwards compatibility standpoint, 
would it be something that could be included in PEP 8?

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[issue43833] Unexpected Parsing of Numeric Literals Concatenated with Boolean Operators

[sco1]

sco1  added the comment:

We can also see this kind of thing with other literals, would that be in scope 
here?

e.g.

```
Python 3.9.4 (default, Apr  5 2021, 12:33:45) 
[Clang 12.0.0 (clang-1200.0.32.29)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> "foo"in ["foo", "bar"]
True
>>> [1,]in [[1,]]
True
```

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[issue43833] Unexpected Parsing of Numeric Literals Concatenated with Boolean Operators

[sco1]

sco1  added the comment:

Makes sense, thanks!

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