CodeQL documentation
CodeQL resources

Wrong number of arguments in a class instantiation

ID: py/call/wrong-number-class-arguments
Kind: problem
Security severity: 
Severity: error
Precision: very-high
Tags:
   - reliability
   - correctness
   - external/cwe/cwe-685
Query suites:
   - python-security-and-quality.qls

Click to see the query in the CodeQL repository

A call to the __init__ method of a class must supply an argument for each parameter that does not have a default value defined, so:

  • The minimum number of arguments is the number of parameters without default values.

  • The maximum number of arguments is the total number of parameters, unless the class __init__ method takes a varargs (starred) parameter in which case there is no limit.

Recommendation

If there are too few arguments then check to see which arguments have been omitted and supply values for those.

If there are too many arguments then check to see if any have been added by mistake and remove those.

Also check where a comma has been inserted instead of an operator or a dot. For example, the code is obj,attr when it should be obj.attr.

If it is not clear which are the missing or surplus arguments, then this suggests a logical error. The fix will then depend on the nature of the error.

Example

class Point(object):
    def __init__(self, x, y):
        self.x = x
        self.y = y

p = Point(1)      # TypeError: too few arguments
p = Point(1,2,3)  # TypeError: too many arguments

References

  • © GitHub, Inc.
  • Terms
  • Privacy