How to read and write files in Python?

Opening a file:

The open() function takes the path to the file and a mode:

• 'r' — read (default)
• 'w' — write (overwrites the file)
• 'a' — append (adds to the end of the file)
• 'rb' / 'wb' — read / write in binary mode

Reading a file:

# Read the entire file
with open("data.txt", "r", encoding="utf-8") as f:
    content = f.read()

# Read line by line
with open("data.txt", "r", encoding="utf-8") as f:
    for line in f:
        print(line.strip())

# Read all lines into a list
with open("data.txt", "r", encoding="utf-8") as f:
    lines = f.readlines()

Writing to a file:

# Overwrite the file
with open("output.txt", "w", encoding="utf-8") as f:
    f.write("First line\n")
    f.write("Second line\n")

# Append to the end
with open("output.txt", "a", encoding="utf-8") as f:
    f.write("Another line\n")

Encodings:

Always specify encoding="utf-8" to avoid issues with special characters and non-Latin alphabets:

# Without specifying encoding, a UnicodeDecodeError might occur
with open("data.txt", "r", encoding="utf-8") as f:
    content = f.read()

Important:

Always use the with statement — it ensures the file is properly closed even if an error occurs.