Python Math Module: isinf() vs isfinite() Explained

Learn the key differences between math.isinf() and math.isfinite() in Python. Understand how to detect infinite, finite, and NaN values effectively using the math module.

Here’s a clear comparison between math.isinf(x) and math.isfinite(x) in Python:

math.isinf(x)

• Purpose: Checks whether a value is infinite.
• Returns: True if x is either positive infinity (+inf) or negative infinity (-inf); otherwise, False.

• Example:

  import math
  print(math.isinf(float('inf')))   # True
  print(math.isinf(10))             # False
  

math.isfinite(x)

• Purpose: Checks whether a value is a finite number.
• Returns: True if x is neither infinite (inf, -inf) nor NaN (Not a Number); otherwise, False.

• Example:

  import math
  print(math.isfinite(10))            # True
  print(math.isfinite(float('inf')))  # False
  print(math.isfinite(float('nan')))  # False
  

Key Differences