python type_error official true

TypeError

ID: python/typeerror

Also available as: JSON · Markdown
80%Fix Rate
95%Confidence
0Evidence

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.x active — — —

Root Cause

An operation or function was applied to an object of inappropriate type. The associated value gives details about the type mismatch.

generic

Official Documentation

https://docs.python.org/3/library/exceptions.html

Workarounds

  1. 90% success Check the expected types of function arguments; use isinstance() for type checking 
    if not isinstance(value, (int, float)): raise TypeError(...)
  2. 90% success Use type annotations and mypy for static type checking before runtime 
    def func(x: int) -> str: ...

Dead Ends

Common approaches that don't work:

  1. Using type() == check instead of isinstance() 80% fail

    Does not account for subclasses; violates Liskov substitution

  2. Forcing type conversion with int()/str() without validation 80% fail

    Silently converts invalid data or raises ValueError in unexpected places