File Handling and Exceptions

Real programs need to interact with the outside world — reading configuration files, processing data, saving results, and handling errors gracefully. In this lesson, you will learn how to read and write files and how to handle exceptions so your programs do not crash unexpectedly.

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Reading Files

The open() Function

# Basic file reading
file = open("data.txt", "r")  # "r" = read mode
content = file.read()          # read entire file as a string
print(content)
file.close()                   # always close the file!

The with Statement (Recommended)

The with statement automatically closes the file, even if an error occurs:

# Much better — file is closed automatically
with open("data.txt", "r") as file:
    content = file.read()
    print(content)
# file is automatically closed here

Always use with for file operations.

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Reading Methods

# read() — read the entire file as one string
with open("data.txt", "r") as f:
    content = f.read()
    print(content)

# readline() — read one line at a time
with open("data.txt", "r") as f:
    first_line = f.readline()
    second_line = f.readline()
    print(first_line.strip())  # strip() removes the newline character