How do you handle CSV files in Python?

Use the csv module: csv.reader/csv.writer for lists, csv.DictReader/csv.DictWriter for dictionaries.

How do you handle JSON files in Python?

Use the json module: json.load() to read file to Python object, json.dump() to write object to file.

What are best practices for Python file handling?

Always use 'with' statement, specify encoding ('utf-8'), handle exceptions, close files properly, use appropriate modes.

Python File Handling: Reading/Writing Text, CSV & JSON Files

Q: How do you read and write text files in Python?

Use open('file.txt', mode) with methods like read(), readline(), readlines() for reading and write(), writelines() for writing.

Q: What is the with statement in Python file handling?

The with statement is a context manager that automatically closes the file after operations, even if an error occurs.

Q: What are file modes in Python?

Modes include 'r' (read), 'w' (write, overwrite), 'a' (append), 'r+' (read/write), and binary variants with 'b' (e.g., 'rb', 'wb').

1. How do you read and write text files in Python?

Q: How to read/write text files?

Reading Text Files: Use the open() function to access a file's contents, then read using methods like read(), readline(), or readlines().

Writing Text Files: Use open() with a write mode, then write using write() or writelines().

Key Methods:

file.read(size): Reads entire file or up to size bytes.
file.readline(): Reads one line.
file.readlines(): Reads all lines into a list.
file.write(string): Writes a string.
file.writelines(lines): Writes a list of strings.

Use Case: Storing logs, reading configuration files, or saving user data.

2. Can you give an example of reading and writing text files?

# Reading and writing text files
# Writing to a file
with open('output.txt', 'w') as file:
    file.write("Hello, Python!\n")
    file.writelines(["Line 1\n", "Line 2\n"])

# Reading from a file
with open('output.txt', 'r') as file:
    content = file.read()
    print("Full content:")
    print(content)

# Reading line by line
with open('output.txt', 'r') as file:
    lines = file.readlines()
    print("Lines as list:")
    print(lines)

Output:

Full content:
Hello, Python!
Line 1
Line 2

Lines as list:
['Hello, Python!\n', 'Line 1\n', 'Line 2\n']

3. What is the with statement in Python file handling?

Q: What is the with statement?

with Statement: A context manager that ensures files are properly opened and closed, even if an error occurs.

Syntax:

with open('file.txt', mode) as file:
    # File operations

Benefits:

Automatically closes the file after operations.
Handles exceptions gracefully.
Simplifies code compared to manual file.close().

Use Case: Safe file operations, preventing resource leaks.

4. Can you give an example of the with statement?

# with statement example
try:
    with open('data.txt', 'w') as file:
        file.write("Sample data\n")
    print("File written successfully")

    with open('data.txt', 'r') as file:
        content = file.read()
        print("File content:")
        print(content)
except FileNotFoundError as e:
    print(f"Error: {e}")

Output:

File written successfully
File content:
Sample data

5. What are file modes in Python?

Q: What are file modes?

File Modes: Specify how a file is opened in the open() function.

Text Modes:

'r': Read (default, raises error if file doesn't exist).
'w': Write (creates/overwrites file).
'a': Append (adds to end, creates if doesn't exist).
'r+': Read and write (file must exist).
'w+': Write and read (creates/overwrites file).
'a+': Append and read (creates if doesn't exist).

Binary Modes: Add b (e.g., 'rb', 'wb') for binary files (e.g., images, CSVs in some cases).

Use Case: Choosing the right mode for reading, writing, or appending data.

6. Can you give an example of different file modes?

# File modes example
# Write mode (w)
with open('modes.txt', 'w') as file:
    file.write("Initial content\n")

# Append mode (a)
with open('modes.txt', 'a') as file:
    file.write("Appended content\n")

# Read mode (r)
with open('modes.txt', 'r') as file:
    print("Read mode content:")
    print(file.read())

# Read and write mode (r+)
with open('modes.txt', 'r+') as file:
    file.write("Updated")
    file.seek(0)  # Move to start
    print("Read after r+ write:")
    print(file.read())

# Binary mode (wb, rb)
with open('binary.bin', 'wb') as file:
    file.write(b"Binary data")

with open('binary.bin', 'rb') as file:
    print("Binary content:")
    print(file.read())

Output:

Read mode content:
Initial content
Appended content

Read after r+ write:
Updated content
Appended content

Binary content:
b'Binary data'

7. How do you handle CSV and JSON files in Python?

Q: How to handle CSV and JSON?

CSV Files: Use the csv module to read/write comma-separated value files.

Methods: csv.reader, csv.writer, csv.DictReader, csv.DictWriter.

JSON Files: Use the json module to read/write JavaScript Object Notation data.

Methods: json.load() (read file), json.dump() (write file), json.loads() (parse string), json.dumps() (create string).

Use Case: Processing structured data (e.g., datasets, configuration files).

8. Examples of CSV and JSON handling + Best Practices

Q: Best practices for file handling?

Always use with open(...) to auto-close files.
Specify encoding: open(..., encoding='utf-8').
Handle exceptions (FileNotFoundError, IOError).
Use csv module for CSV to handle quoting/escaping.
Use json for structured data interchange.
Avoid hardcoding file paths; use os.path or pathlib.