Confusing octal literal¶

ID: py/old-style-octal-literal
Kind: problem
Security severity: 
Severity: recommendation
Precision: high
Tags:
   - readability
Query suites:
   - python-security-and-quality.qls

Click to see the query in the CodeQL repository

Octal literals starting with 0 are easily misread as a decimal, particularly by those programmers who do not have a C or Java background.

The new literal syntax for non-decimal numbers is more distinct and is thus less likely to be misunderstood.

Recommendation¶

Use the 0oXXX form instead of the 0XXX form. Alternatively use binary or hexadecimal format if that would be clearer.

Example¶

#Easily misread as x = 15
x = 015

#The extra 'o' alerts the reader that this is an octal literal
y = 0o15

#If this is a byte sized value then a hexadecimal might be clearer
y = 0x0d

#Or if it is a bit pattern then a binary value might be clearer
y = 0b1101

References¶

Python Language Reference: Integer Literals.
Python PEP 3127: Integer Literal Support and Syntax.

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