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 which works today might be broken tomorrow.
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.
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
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.
Resources
