Day 13 45 min beginner

Working with Files

Learn how to store data permanently by reading and writing text files

Learning Objectives

  • Open, read, and close text files
  • Write and append data to files
  • Use the 'with' statement for safe file handling
  • Understand different file modes (r, w, a)

Persistent Data

Until now, all our data disappeared as soon as the program stopped. To save data for later, we need to use Files.

Opening and Closing Files

Python has a built-in open() function. You must always close() a file when you are done to free up resources.

manual_file.py 
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file = open("test.txt", "r") # 'r' means read
content = file.read()
print(content)
file.close() # Don't forget this!

Closing files manually is risky—if an error happens, the file might stay open. The with statement handles this automatically.

with_example.py 
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with open("test.txt", "r") as file:
    content = file.read()
    print(content)
# File is automatically closed here!

File Modes

Mode Description
r Read (Default). Error if file doesn’t exist.
w Write. Overwrites the file if it exists. Creates it if not.
a Append. Adds to the end of the file. Creates it if not.
x Create. Fails if the file already exists.

Writing to a File

writing.py 
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# Overwriting/Creating
with open("new_file.txt", "w") as f:
    f.write("Hello World!\n")
    f.write("This is a new line.")

# Appending
with open("new_file.txt", "a") as f:
    f.write("\nAdding one more line.")

Interactive Practice

Try writing a program that asks for a user’s name and saves it to a file called users.txt.

flowchart LR Input[Get User Name] --> Open[Open users.txt in 'a' mode] Open --> Write[write name + \n] Write --> Close[Close File automatically]

Quiz

Complete this quiz with a minimum score of 80% to mark Day 13 as complete.

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Discussion

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