File modes and access types in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to open a file named 'data.txt' for reading.

Python

file = open('data.txt', '[1]')

Drag options to blanks, or click blank then click option'

Ax

Bw

Ca

Dr

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'w' which opens the file for writing and erases content.

Using 'a' which opens the file for appending.

The mode 'r' opens the file for reading only.

2fill in blank

medium

Complete the code to open a file named 'log.txt' for appending new data.

Python

file = open('log.txt', '[1]')

Drag options to blanks, or click blank then click option'

Aa

Bx

Cw

Dr

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'w' which overwrites the file content.

Using 'r' which only reads and does not allow writing.

The mode 'a' opens the file for appending, so new data is added at the end.

3fill in blank

hard

Fix the error in the code to open a file for writing only if it does not exist.

Python

file = open('newfile.txt', '[1]')

Drag options to blanks, or click blank then click option'

Ar

Bx

Cw

Da

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'w' which overwrites existing files.

Using 'a' which appends to existing files.

The mode 'x' creates a new file and opens it for writing, but fails if the file already exists.

4fill in blank

hard

Fill both blanks to open a file named 'report.txt' for reading and writing.

Python

file = open('report.txt', '[1][2]')

Drag options to blanks, or click blank then click option'

Ar

Bw

C+

Da

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'w+' which truncates the file before writing.

Using 'a+' which opens for appending and reading.

The mode 'r+' opens the file for both reading and writing without truncating it.

5fill in blank

hard

Fill the blanks to create a dictionary comprehension that maps filenames to their sizes only if size is greater than 1000 bytes.

Python

sizes = {filename: os.path.getsize(filename) for filename in files if os.path.getsize(filename) [1] [2]

Drag options to blanks, or click blank then click option'

A>

B1000

C==

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' which checks for exact size.

Using '<' which checks for smaller sizes.

The condition checks if the file size is greater than 1000 bytes, so the operator is '>' and the number is 1000.

Practice

1. Which file mode in Python opens a file for reading only, and raises an error if the file does not exist?
file = open('data.txt', mode)

easy

A. "r"

B. "w"

C. "a"

D. "x"

Solution

1. Step 1: Understand the purpose of mode "r"

   Mode "r" opens a file for reading only and requires the file to exist.

2. Step 2: Compare with other modes

   Mode "w" opens for writing (creates or truncates), "a" appends, and "x" creates a new file but errors if it exists.

3. Final Answer:

   "r" -> Option A

4. Quick Check:

   Read-only mode = "r" [OK]

Hint: Read-only mode is just "r" [OK]

Common Mistakes:

• Confusing "r" with "w" which overwrites files
• Using "a" thinking it reads
• Choosing "x" which creates files

2. Which of the following is the correct syntax to open a file named log.txt for appending text in Python?

easy

A. open('log.txt', 'r')

B. open('log.txt', 'w')

C. open('log.txt', 'a')

D. open('log.txt', 'x')

Solution

1. Step 1: Identify the mode for appending

   Mode "a" opens the file for appending, adding new content at the end.

2. Step 2: Check syntax correctness

   The syntax open('log.txt', 'a') is correct for appending text.

3. Final Answer:

   open('log.txt', 'a') -> Option C

4. Quick Check:

   Append mode = "a" [OK]

Hint: Append mode is always "a" [OK]

Common Mistakes:

• Using "r" which is read-only
• Using "w" which overwrites the file
• Using "x" which creates new file only

3. What will be the output of the following code if example.txt contains the text "Hello"?

with open('example.txt', 'w') as f:
    f.write('World')

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

medium

A. World

B. Hello

C. HelloWorld

D. Error

Solution

1. Step 1: Understand mode "w" effect on file content

   Opening with "w" overwrites the file, so "World" replaces "Hello".

2. Step 2: Reading the file after writing

   Reading the file after writing will output the new content "World".

3. Final Answer:

   World -> Option A

4. Quick Check:

   Write mode overwrites content = "World" [OK]

Hint: Write mode "w" replaces file content [OK]

Common Mistakes:

• Assuming "w" appends instead of overwrites
• Expecting original content to remain
• Thinking reading causes error after writing

4. What is wrong with this code snippet?

f = open('data.txt', 'r')
content = f.read()
f.write('More data')
f.close()

medium

A. No error, code is correct

B. File is not closed properly

C. File mode should be "a" to read

D. File is opened in read mode but write is attempted

Solution

1. Step 1: Check file mode and operations

   The file is opened in "r" (read) mode, which does not allow writing.

2. Step 2: Identify the error cause

   Calling f.write() in read mode causes a runtime error because writing is not allowed.

3. Final Answer:

   File is opened in read mode but write is attempted -> Option D

4. Quick Check:

   Write not allowed in "r" mode [OK]

Hint: Write needs "w" or "a" mode, not "r" [OK]

Common Mistakes:

• Forgetting write is disallowed in read mode
• Not closing file properly (though here it is closed)
• Confusing append mode with read mode

5. You want to create a new file report.txt but only if it does not already exist. Which mode should you use to avoid overwriting existing files?

hard

A. "w"

B. "x"

C. "a"

D. "r+"

Solution

1. Step 1: Understand mode "x" behavior

   Mode "x" creates a new file and raises an error if the file already exists, preventing overwriting.

2. Step 2: Compare with other modes

   "w" overwrites, "a" appends or creates, "r+" opens for reading and writing but requires file to exist.

3. Final Answer:

   "x" -> Option B

4. Quick Check:

   Create new only = "x" mode [OK]

Hint: Use "x" to create file only if not exists [OK]

Common Mistakes:

• Using "w" which overwrites existing files
• Using "a" which appends or creates silently
• Using "r+" which needs existing file