Python File Input and Output Questions and Answers

Question 1

Which of the following is the most idiomatic and safest way to open a file for writing in Python, ensuring that it is always closed properly?

Accepted Answer

with open('data.txt', 'w') as file:
    file.write('content')

Answer

file = open('data.txt', 'w'); file.write('content'); file.close()

Answer

try:
    file = open('data.txt', 'w')
    file.write('content')
finally:
    file.close()

Answer

def write_file():
    file = open('data.txt', 'w')
    file.write('content')
    return file.close()

Question 2

A developer needs to write a logging function that adds new entries to the end of a log file. If the log file does not exist, it should be created. The function also needs to be able to read from the file to check previous logs. Which file mode is the most appropriate for this scenario?

Accepted Answer

'a+'

Answer

'w+'

Answer

'r+'

Answer

'a'

Question 3

What is the primary difference in the return value between the `read()` and `readlines()` file methods in Python?

Accepted Answer

`read()` returns a single string containing the entire file content, while `readlines()` returns a list of strings, where each string is a line from the file.

Answer

`read()` returns a list of lines, while `readlines()` returns a single string containing the entire file content.

Answer

`read()` returns a generator object for iterating over lines, while `readlines()` loads all lines into memory at once.

Answer

Both methods return a list of strings, but `readlines()` includes newline characters while `read()` does not.

Question 4

After executing the following code, what will be the content of 'report.txt'?

```python
lines = ['- Item 1', '- Item 2', '- Item 3']
with open('report.txt', 'w') as f:
    f.writelines(lines)
```

Accepted Answer

- Item 1- Item 2- Item 3

Answer

- Item 1
- Item 2
- Item 3

Answer

- Item 1 - Item 2 - Item 3

Answer

['- Item 1', '- Item 2', '- Item 3']

Question 5

Given a file named 'data.txt' containing the text 'ABCDEFG', what will the following Python code print?

```python
with open('data.txt', 'r') as f:
    f.read(3)
    f.seek(1)
    print(f.read(2))
```

Accepted Answer

BC

Answer

AB

Answer

DE

Answer

CD

Question 6

A developer needs to save a Python dictionary to a file so it can be perfectly reconstructed into a dictionary object later. Which module and file mode should be used for this task?

Accepted Answer

The `pickle` module with the `'wb'` mode.

Answer

The `json` module with the `'w'` mode.

Answer

The `os` module with the `'wb'` mode.

Answer

The `sys` module with the `'w'` mode.