CodeQL documentation

Missing named arguments in formatting call

ID: py/str-format/missing-named-argument
Kind: problem
Severity: error
Precision: high
Tags:
   - reliability
   - correctness
Query suites:
   - python-security-and-quality.qls

Click to see the query in the CodeQL repository

A formatting expression, that is an expression of the form the_format.format(args) or format(the_format, args), can use named fields. If it does, then keyword arguments must be supplied for all named fields. If any of the keyword arguments are missing then a KeyError will be raised.

Recommendation

Change the format to match the arguments and ensure that the arguments have the correct names.

Example

In the following example, if unlikely_condition() is true, then a KeyError will be raised as the keyword parameter eggs is missing. Adding a keyword parameter named eggs would fix this.

def unsafe_named_format():
    the_format = "{spam} {eggs}"
    if unlikely_condition():
        return the_format.format(spam="spam", completely_different="eggs")
    else:
        return the_format.format(spam="spam", eggs="eggs")

References