Summary - File I/O
- Python course
- Intermediate
- Lesson 69/116
- 5 min
Combine with, read and write to write a notes app.
Summary - File I/O
In this group you learned file opening, reading, writing, the with statement and modes. open returns a file object; encoding="utf-8" keeps Turkish text safe. read returns all content, readline one line, readlines a list of lines.
For writing, write writes one string and writelines a list of strings. The with block closes the file automatically at exit; that's why it's always preferred. Modes: r, w, a, x; add b for binary.
Mini task: keep a diary
As a summary you'll write a small diary app. With w mode you open the file and write the first line; with a mode you append the second line; with r mode you read the whole content as one string and print it.
You use three separate with blocks. The output has two lines; the \n markers stay in the file. This task shows how the modes work together.
Practice Three-mode diary
Write three with blocks. First with open("diary.txt", "w", encoding="utf-8") as f: f.write("Monday\n"). Second with open("diary.txt", "a", encoding="utf-8") as f: f.write("Tuesday\n"). Third with open("diary.txt", "r", encoding="utf-8") as f: print(f.read(), end=""). The output has two lines; pass end="" to print to avoid an extra line.
Starter code
# w mode: write Monday
# a mode: append Tuesday
# r mode: print all content (end="")Sample solution
# w mode: write Monday
with open("diary.txt", "w", encoding="utf-8") as f:
f.write("Monday\n")
# a mode: append Tuesday
with open("diary.txt", "a", encoding="utf-8") as f:
f.write("Tuesday\n")
# r mode: print all content (end="")
with open("diary.txt", "r", encoding="utf-8") as f:
print(f.read(), end="")Expected output
Monday Tuesday
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What is the best practice in file operations?
- Skip the close call
- Always prefer binary mode
- Use the with statement Correct answer
- Skip the encoding parameter
Explanation: The with statement provides automatic closing; that's the best practice.
2 Complete the with statement
____ open("f.txt", "w", encoding="utf-8") as f:
f.write("Hello")with open("f.txt", "w", encoding="utf-8") as f:
f.write("Hello")Explanation: The with statement closes the file automatically.
3 Match the file operations
| Term | Meaning |
|---|---|
open |
Opens a file |
with |
Closes automatically |
read |
Reads content |
write |
Writes content |