How Does Python 2 Compare Objects of Different Types?

How Object Comparison Works in Python 2

Python 2's behavior when comparing objects of different types can be confusing, but it's based on implementation details provided by the language specification.

Implementation-Specific Behavior

When comparing objects of different types, Python 2 uses the following order:

• Numerics first: Numeric types (integers, floats) take precedence over non-numerics.
• Lexicographic ordering for strings: Strings are compared lexicographically.
• Type name ordering for non-numerics: Objects of the same type but with no proper comparison methods are ordered by their type names, sorted alphabetically.

Examples

To illustrate:

print "100" < "2"      # True (lexicographic)
print "5" > "9"        # False (lexicographic)

print "100" < 2        # False (numeric first)
print 100 < "2"        # True (numeric first, lexicographic second)

print 5 > "9"          # False (lexicographic)
print "5" > 9          # True (numeric first, lexicographic second)

print [] > float('inf') # True (non-numeric ordering)
print () > []          # True (non-numeric ordering)

Implementation Details

This behavior is mandated by the CPython implementation of Python 2. The language spec states that objects of different types are ordered "arbitrarily but consistently," leaving the details up to the implementation.

Differences Between Versions and Implementations

In Python 3, comparisons between integers and strings raise an error. Other implementations of Python may also have slightly different behavior.

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