Package structure and usage in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of importing a submodule

Consider this package structure:

mypackage/
  __init__.py
  module_a.py
  subpackage/
    __init__.py
    module_b.py

In module_b.py, there is a function def greet(): return 'Hello from B'.

What is the output of this code?

from mypackage.subpackage import module_b
print(module_b.greet())

Python

from mypackage.subpackage import module_b
print(module_b.greet())

A ModuleNotFoundError

B AttributeError

C ImportError

D Hello from B

💡 Hint

Think about how Python imports functions from submodules inside packages.

Importing the submodule module_b from mypackage.subpackage works if the package structure is correct and greet() is defined there. Calling module_b.greet() returns the string as expected.

❓ Predict Output

intermediate

Effect of __init__.py on package import

Given this package structure:

mypackage/
  __init__.py
  utils.py

and __init__.py contains:

from .utils import helper

and utils.py contains:

def helper():
    return 'Helping'

What is the output of this code?

import mypackage
print(mypackage.helper())

Python

import mypackage
print(mypackage.helper())

A Helping

B AttributeError

C ImportError

D NameError

💡 Hint

Check what __init__.py exposes when importing the package.

The __init__.py imports helper from utils and makes it available as mypackage.helper. So calling mypackage.helper() works and returns 'Helping'.

🔧 Debug

advanced

Why does this import fail?

You have this package structure:

mypackage/
  __init__.py
  tools.py

In tools.py you have:

def tool():
    return 'Tool here'

You run this code from outside the package folder:

from mypackage import tool
print(tool())

But it raises an error. What is the error?

Python

from mypackage import tool
print(tool())

A AttributeError

B ImportError

C ModuleNotFoundError

D NameError

💡 Hint

Check what names are exposed by mypackage when importing.

The package mypackage does not expose tool directly because __init__.py does not import tool. So from mypackage import tool raises ImportError.

📝 Syntax

advanced

Correct relative import syntax inside a package

Inside mypackage/subpackage/module_c.py, you want to import func from mypackage/module_a.py.

Which import statement is correct?

A from ..module_a import func

B from .module_a import func

C import module_a.func

D from mypackage.module_a import func

💡 Hint

Think about how many levels up you need to go to reach module_a.

Since module_c.py is inside subpackage, to import from module_a.py in the parent package, you use two dots .. to go up one level: from ..module_a import func.

🚀 Application

expert

Number of modules loaded after import

Given this package structure:

mypackage/
  __init__.py
  alpha.py
  beta.py
  gamma/
    __init__.py
    delta.py

Where:
- __init__.py in mypackage imports alpha and gamma
- __init__.py in gamma imports delta

What is the total number of distinct modules loaded into memory after running:

import mypackage

Python

import mypackage

A 3

B 1

C 4

D 2

💡 Hint

Count the modules explicitly imported during the package import.

Importing mypackage runs its __init__.py, which imports alpha and gamma. Importing gamma runs its __init__.py, which imports delta. So modules loaded are: mypackage, alpha, gamma, and delta. Total 4 modules.