Why is this an issue?

Importing every public name from a module using a wildcard (from mymodule import *) is a bad idea because:

• It could lead to conflicts between names defined locally and the ones imported.
• It reduces code readability as developers will have a hard time knowing where names come from.
• It clutters the local namespace, which makes debugging more difficult.

Remember that imported names can change when you update your dependencies. A wildcard import that works today might be broken tomorrow.

Exceptions

No issue will be raised in __init__.py files. Wildcard imports are a common way of populating these modules.

No issue will be raised in modules doing only imports. Local modules are sometimes created as a proxy for third-party modules.

# file: mylibrary/pyplot.py
try:
    from guiqwt.pyplot import *  # Ok
except Exception:
    from matplotlib.pyplot import *  # Ok

Just keep in mind that wildcard imports might still create issues in these cases. It’s always better to import only what you need.

How to fix it

There are two ways to avoid a wildcard import:

• Replace it with import mymodule and access module members as mymodule.myfunction. If the module name is too long, alias it to a shorter name. Example: import pandas as pd
• List every imported name. If necessary import statements can be split on multiple lines using parentheses (preferred solution) or backslashes.

Code examples

Noncompliant code example

from math import *  # Noncompliant
def exp(x):
    pass
print(exp(0))   # "None" will be printed

Compliant solution

import math
def exp(x):
    pass
print(math.exp(0))   # "1.0" will be printed

Or

from math import exp as m_exp
def exp(x):
    pass
print(m_exp(0))   # "1.0" will be printed

Resources

• Python documentation - The import statement