File system interaction basics in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Reading a file's content

What is the output of this code if the file example.txt contains the text Hello World?

Python

with open('example.txt', 'r') as f:
    content = f.read()
print(content)

A "Hello World"

B ['Hello World']

C b'Hello World'

D None

💡 Hint

The read() method returns the whole file content as a string.

The open function with mode 'r' opens the file for reading as text. The read() method reads the entire content as a string. So the output is the exact text inside the file.

❓ Predict Output

intermediate

Writing and reading back a file

What will be printed after running this code?

Python

with open('testfile.txt', 'w') as f:
    f.write('12345')
with open('testfile.txt', 'r') as f:
    print(f.readline())

A 12345

B ['12345']

C None

D 1

💡 Hint

The write method writes text, and readline reads one line as a string.

The file is written with the string 12345. Then reading one line returns the whole string since there is no newline. So it prints 12345.

❓ Predict Output

advanced

Using os.path to check file existence

What does this code print if the file data.txt does NOT exist in the current folder?

Python

import os
if os.path.exists('data.txt'):
    print('Found')
else:
    print('Not Found')

A Found

B Not Found

C Raises FileNotFoundError

D None

💡 Hint

The os.path.exists function returns True if the file exists, otherwise False.

Since the file does not exist, os.path.exists returns False, so the else branch prints Not Found.

❓ Predict Output

advanced

Understanding file modes and errors

What error does this code raise if readonly.txt exists but is read-only?

Python

with open('readonly.txt', 'w') as f:
    f.write('Trying to write')

A No error, writes successfully

B TypeError

C PermissionError

D FileNotFoundError

💡 Hint

Opening a read-only file for writing usually causes a permission error.

Trying to open a file with write mode 'w' when the file is read-only causes a PermissionError because the program lacks permission to modify the file.

🧠 Conceptual

expert

File pointer position after reading

After running this code, what is the value of pos?

Python

with open('numbers.txt', 'w') as f:
    f.write('1234567890')
with open('numbers.txt', 'r') as f:
    f.read(4)
    pos = f.tell()
print(pos)

A 10

B 0

C Raises an error

D 4

💡 Hint

The tell() method returns the current position of the file pointer.

The read(4) reads 4 characters, moving the file pointer 4 positions forward. So tell() returns 4.