Working with JSON files in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

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

Python

with open('data.json', [1]) as file:
    data = file.read()

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

A'w'

B'r'

C'a'

D'x'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'w' instead of 'r' will overwrite the file.

Using 'a' opens the file for appending, not reading.

To read a file, you use mode 'r'.

2fill in blank

medium

Complete the code to load JSON data from a file object named 'file'.

Python

import json

data = json.[1](file)

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

Aload

Bdump

Cloads

Ddumps

Attempts:

3 left

💡 Hint

Common Mistakes

Using dump or dumps which are for writing JSON.

Using loads which expects a string, not a file.

The function json.load() reads JSON data from a file object.

3fill in blank

hard

Fix the error in the code to write a Python dictionary 'data' to a JSON file named 'output.json'.

Python

import json

with open('output.json', 'w') as file:
    json.[1](data, file)

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

Adump

Bloads

Cload

Ddumps

Attempts:

3 left

💡 Hint

Common Mistakes

Using load or loads which are for reading JSON.

Using dumps without writing the string to the file.

Use json.dump() to write JSON data to a file.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps each word to its length, but only for words longer than 3 characters.

Python

words = ['apple', 'bat', 'carrot', 'dog']
lengths = {word: [1] for word in words if [2]

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

Alen(word)

Bword

Clen(word) > 3

Dword > 3

Attempts:

3 left

💡 Hint

Common Mistakes

Using the word itself as the value instead of its length.

Comparing the word string directly to 3, which is invalid.

The dictionary maps each word to its length using len(word). The condition filters words with length greater than 3.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that converts keys to uppercase, keeps values, and filters only items where value is greater than 10.

Python

data = {'a': 5, 'b': 15, 'c': 20}
result = { [1]: [2] for k, v in data.items() if [3] }

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

Ak.upper()

Bv

Cv > 10

Dk

Attempts:

3 left

💡 Hint

Common Mistakes

Using the original key without converting to uppercase.

Filtering with incorrect conditions like k > 10.

The comprehension creates a new dictionary with uppercase keys, original values, and includes only items where the value is greater than 10.

Practice

1.

What is the main purpose of using JSON files in Python programs?

easy

A. To create graphical user interfaces

B. To execute Python code faster

C. To save and load data in a simple text format

D. To compile Python programs into executables

Solution

1. Step 1: Understand JSON file usage

   JSON files store data in a text format that is easy to read and share.

2. Step 2: Identify the correct purpose

   Saving and loading data simply matches the main use of JSON files in Python.

3. Final Answer:

   To save and load data in a simple text format -> Option C

4. Quick Check:

   JSON files = data storage [OK]

Hint: JSON files store data simply as text [OK]

Common Mistakes:

• Thinking JSON speeds up code execution
• Confusing JSON with GUI creation
• Assuming JSON compiles code

2.

Which of the following is the correct way to open a JSON file named data.json for reading in Python?

easy

A. open('data.json', 'r')

B. open('data.json', 'w')

C. open('data.json', 'a')

D. open('data.json', 'x')

Solution

1. Step 1: Understand file modes

   'r' mode opens a file for reading, 'w' for writing, 'a' for appending, 'x' for creating new file.

2. Step 2: Choose mode for reading JSON

   To read JSON data, the file must be opened in 'r' mode.

3. Final Answer:

   open('data.json', 'r') -> Option A

4. Quick Check:

   Read mode = 'r' [OK]

Hint: Use 'r' mode to read files [OK]

Common Mistakes:

• Using 'w' which overwrites the file
• Using 'a' which appends data
• Using 'x' which fails if file exists

3.

What will be the output of the following Python code?

import json

with open('data.json', 'w') as f:
    json.dump({'name': 'Alice', 'age': 30}, f)

with open('data.json', 'r') as f:
    data = json.load(f)
print(data['age'])

medium

A. Alice

B. 30

C. {'name': 'Alice', 'age': 30}

D. Error: file not found

Solution

1. Step 1: Write dictionary to JSON file

   The code writes {'name': 'Alice', 'age': 30} to 'data.json' using json.dump.

2. Step 2: Read JSON file and access 'age'

   json.load reads the file back as a dictionary, then data['age'] accesses the value 30.

3. Final Answer:

   30 -> Option B

4. Quick Check:

   data['age'] = 30 [OK]

Hint: json.load returns Python dict from JSON file [OK]

Common Mistakes:

• Expecting string output instead of integer
• Confusing json.dump and json.load usage
• Assuming file read fails without writing first

4.

Identify the error in this code snippet that tries to read JSON data from a file:

import json

f = open('data.json', 'r')
data = json.load(f)
f.close()
print(data)

medium

A. Missing import statement for json

B. File not opened in write mode

C. File not closed properly

D. No error, code works correctly

Solution

1. Step 1: Check import and file open

   The code imports json and opens the file in 'r' mode correctly.

2. Step 2: Verify json.load and file close

   json.load reads JSON data properly, and file is closed with f.close().

3. Final Answer:

   No error, code works correctly -> Option D

4. Quick Check:

   Code reads JSON file correctly [OK]

Hint: json.load needs file opened in 'r' mode [OK]

Common Mistakes:

• Forgetting to import json
• Opening file in wrong mode
• Not closing the file after reading

5.

You want to save a Python dictionary {'a': 1, 'b': 2, 'c': 3} to a JSON file and then read it back. Which code snippet correctly does this and prints the value of key 'b'?

hard

A. import json
with open('file.json', 'w') as f:
json.dump({'a': 1, 'b': 2, 'c': 3}, f)
with open('file.json', 'r') as f:
data = json.load(f)
print(data['b'])

B. import json
with open('file.json', 'r') as f:
json.dump({'a': 1, 'b': 2, 'c': 3}, f)
with open('file.json', 'w') as f:
data = json.load(f)
print(data['b'])

C. import json
f = open('file.json', 'w')
json.load({'a': 1, 'b': 2, 'c': 3}, f)
f.close()
f = open('file.json', 'r')
data = json.dump(f)
f.close()
print(data['b'])

D. import json
with open('file.json', 'w') as f:
json.load({'a': 1, 'b': 2, 'c': 3}, f)
with open('file.json', 'r') as f:
data = json.dump(f)
print(data['b'])

Solution

1. Step 1: Write dictionary to JSON file correctly

   json.dump writes Python dict to file opened in 'w' mode.

   import json
   with open('file.json', 'w') as f:
       json.dump({'a': 1, 'b': 2, 'c': 3}, f)
   with open('file.json', 'r') as f:
       data = json.load(f)
   print(data['b'])

   does this correctly.

2. Step 2: Read JSON file and access key 'b'

   json.load reads JSON back from file opened in 'r' mode, then data['b'] prints 2.

3. Final Answer:

   Code in Option A correctly saves and reads JSON, printing 2 -> Option A

4. Quick Check:

   json.dump to write, json.load to read [OK]

Hint: Use json.dump to write, json.load to read JSON files [OK]

Common Mistakes:

• Using json.load to write data
• Using json.dump to read data
• Opening files in wrong modes