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How to Check If a Module Has a Specific Attribute in Python

When working with dynamic imports, plugins, or introspection, you often need to check if a module (or any object) contains a specific attribute (be it a function, class, or variable) before attempting to use it. Accessing a non-existent attribute raises an AttributeError.

This guide covers how to safely check for and retrieve attributes using hasattr() and getattr().

Method 1: Using hasattr() (Boolean Check)​

The built-in hasattr(object, name) function is the most direct way to check for existence. It returns True if the attribute exists and False otherwise.

import math

# ✅ Check if 'sqrt' exists in the math module
if hasattr(math, 'sqrt'):
    print("Math module has 'sqrt'.")
else:
    print("Math module does not have 'sqrt'.")

# Check for a non-existent attribute
if hasattr(math, 'unknown_func'):
    print("Found 'unknown_func'.")
else:
    print("'unknown_func' not found.")

Output:

Math module has 'sqrt'.
'unknown_func' not found.

Method 2: Using getattr() (Safe Access)​

If your goal is to use the attribute if it exists, getattr(object, name, default) is often cleaner than hasattr. It attempts to get the attribute and returns a default value if it's missing.

import math

# ✅ Get 'pi' safely. If missing, return 3.14
pi_val = getattr(math, 'pi', 3.14)
print(f"PI: {pi_val}")

# Try getting a missing attribute with a default
magic_num = getattr(math, 'magic_number', 0)
print(f"Magic Number: {magic_num}")

Output:

PI: 3.141592653589793
Magic Number: 0
tip

This pattern is excellent for optional dependencies or configuration modules where settings might be missing.

Method 3: Exception Handling (EAFP)​

Python often encourages the "Easier to Ask for Forgiveness than Permission" (EAFP) style. Instead of checking first, just try to use it and catch the error.

import math

try:
    # ⛔️ Warning: 'super_log' doesn't exist
    result = math.super_log(10)
except AttributeError:
    print("Attribute 'super_log' not found. Using default logic.")
    result = math.log(10)

print(f"Result: {result}")

Output:

Attribute 'super_log' not found. Using default logic.
Result: 2.302585092994046

Method 4: Inspecting __dict__​

You can inspect the module's namespace directly using its __dict__ attribute or the dir() function. This is useful for debugging or filtering attributes.

import math

# ✅ Check if key exists in the module's namespace dictionary
if 'cos' in math.__dict__:
    print("'cos' is available.")

# Using dir()
all_attributes = dir(math)
if 'sin' in all_attributes:
    print("'sin' is available.")

Output:

'cos' is available.
'sin' is available.

Conclusion​

To check for attributes in a Python module:

  1. Use hasattr(mod, 'attr') for simple True/False checks.
  2. Use getattr(mod, 'attr', default) when you want to retrieve the value safely with a fallback.
  3. Use try...except AttributeError when you want to execute logic immediately and handle failures gracefully.

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