Reading & Writing Files0%
Reading & Writing Files
Beginner8 min read•Updated: 2026-09-03
Reading & Writing Files
Write lines of text cleanly and inspect file content dynamically.
Key Concepts & Detailed Explanation
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Code Examples & Output
Python
lines_to_write = [
"Chapter 1: Python Basics\n",
"Chapter 2: Data Structures\n",
"Chapter 3: File Handling\n"
]
# Writing multiple lines
with open("chapters.txt", "w") as f:
f.writelines(lines_to_write)
# Reading back line by line
with open("chapters.txt", "r") as f:
for line in f:
print("->", line.strip())
Expected Output:
Output
-> Chapter 1: Python Basics
-> Chapter 2: Data Structures
-> Chapter 3: File Handling
Best Practices & Common Pitfalls
Iterating directly over a file object ('for line in f:') reads memory-efficiently line by line without loading the whole file into RAM.
Practice Quiz
1. Does f.writelines() automatically append newline characters (\n) to each list item?
- A) Yes
- B) No, you must include '\n' in each string explicitly
- C) Only in Python 3
- D) Only with strip()
Answer: B
Explanation: writelines() does not append newlines automatically.
2. Why is 'for line in file:' better than 'file.read().splitlines()' for large files?
- A) It reads line by line lazily, avoiding high memory consumption
- B) It automatically translates uppercase
- C) It creates threads
- D) It is faster on disk
Answer: A
Explanation: Streaming line by line prevents out-of-memory errors on massive files.
Practice Challenge
Write a program that prompts user for their favorite 3 hobbies and writes each to 'hobbies.txt'.
Next Lesson
Working with open()
Continue learning with hands-on practice, examples, and exercises in the upcoming topic.
Related Lessons
| Previous Lesson | Next Lesson |
|---|---|
| Opening & Closing Files | Working with open() |
Practice Quiz
Test your understanding of this lesson with 1 questions. Each question has one correct answer.