File Handling

9 Topics

Opening and Closing Files

open() function, file modes, and proper cleanup

Essential — tests understanding of file I/O, resource management, and the with statement

Reading Files

read, readline, readlines, and iteration methods

File input — tests understanding of memory-efficient reading and different reading strategies

Writing Files

write, writelines, and file output patterns

File output — tests understanding of write modes, buffering, and efficient output

File Modes

Understanding r, w, a, b, x, and + modes

File access — tests understanding of mode combinations and when each is appropriate

with Statement for Files

Context managers and the with statement for safe, automatic resource cleanup when working with files and other resources.

Essential best practice — interviewers expect you to use with for file handling and understand the context manager protocol.

Binary Files

Reading and writing non-text data (images, audio, serialized objects) using binary mode and the struct module for precise byte-level control.

Tests understanding of bytes vs strings, encoding, and low-level data manipulation — common in systems programming interviews.

JSON Files

Comprehensive JSON handling in Python — serialization, deserialization, custom encoders/decoders, working with JSON Lines, and streaming large JSON data.

JSON is the universal data interchange format — interviewers test your ability to parse, generate, and manipulate JSON data efficiently.

CSV Files

Comprehensive CSV handling — reader/writer, DictReader/DictWriter, custom dialects, and processing large CSV files efficiently.

CSV processing is common in data engineering and backend interviews — know both basic and DictReader approaches.

pathlib Module

Modern, object-oriented filesystem path manipulation — path construction, file operations, directory traversal, and glob patterns using the pathlib module.

pathlib is the modern standard for path handling in Python 3 — interviewers prefer it over os.path for cleaner, cross-platform code.