Import statement behavior in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of importing a module with side effects

What is the output when running this code?

Python

import math
print(math.pi)
import math
print(math.sqrt(16))

A

4.0
4.0

B

3.141592653589793
3.141592653589793

C

3.141592653589793
4.0

D Error: module math cannot be imported twice

💡 Hint

Remember that importing a module twice does not reload it.

The math module is imported once. The second import does nothing. math.pi prints 3.141592653589793 and math.sqrt(16) prints 4.0.

❓ Predict Output

intermediate

Effect of import * on namespace

What is the output of this code?

Python

from math import *
print(sin(0))
print(cos(0))

A

sin
cos

B

0
0

C Error: sin is not defined

D

0.0
1.0

💡 Hint

import * brings all functions into current namespace.

sin(0) returns 0.0 and cos(0) returns 1.0 from the math module.

❓ Predict Output

advanced

Importing a module with circular dependency

Given two modules a.py and b.py where each imports the other, what error occurs when running a.py?

Python

a.py:
import b
x = 5

b.py:
import a
y = 10

A AttributeError: partially initialized module 'a' has no attribute 'x'

B No error, runs fine

C SyntaxError: circular import not allowed

D ImportError: cannot import name 'a' from 'b'

💡 Hint

Circular imports without accessing attributes during module initialization do not cause errors.

Python handles circular imports by providing the partially initialized module object. Since b.py does not access any attributes from a.py during its initialization, no AttributeError occurs, and the program runs fine.

❓ Predict Output

advanced

Effect of import aliasing on variable access

What is the output of this code?

Python

import math as m
print(m.sqrt(25))
print(math.sqrt(25))

A

5.0
NameError: name 'math' is not defined

B

5.0
5.0

C

NameError: name 'm' is not defined
5.0

D Error: cannot use alias and original name together

💡 Hint

Aliasing changes the module name in current scope.

math is not defined because it was imported as m. m.sqrt(25) prints 5.0 but math.sqrt(25) raises NameError.

🧠 Conceptual

expert

Understanding import caching behavior

Which statement best describes Python's import caching behavior?

A Modules are loaded once and cached in sys.modules for reuse.

B Modules cannot be imported more than once in a program.

C Modules are loaded from disk every time they are imported.

D Modules are reloaded automatically if their source code changes.

💡 Hint

Think about how Python avoids repeated work when importing.

Python loads a module once and stores it in sys.modules. Subsequent imports use the cached module, improving performance.