Python File Handling

Why File Handling Matters

Many programs need to read data from files or write results to files. Python gives you the open() function for working with files.

file = open("notes.txt", "r")
content = file.read()
file.close()

This works, but it is easy to forget close(). A better pattern is a context manager.

Using with open(...)

The with statement closes the file automatically, even if an error happens inside the block.

with open("notes.txt", "r", encoding="utf-8") as file:
    content = file.read()

print(content)

This is the recommended style for most beginner and intermediate file work.

File Modes

The second argument to open() is the mode.

• "r" reads an existing file.
• "w" writes to a file and replaces old content.
• "a" appends to the end of a file.
• "x" creates a new file and fails if it already exists.

Use write mode carefully because it overwrites the file.

with open("result.txt", "w", encoding="utf-8") as file:
    file.write("Practice complete")

Reading Lines

Use read() to read the whole file, or loop over the file line by line.

with open("names.txt", "r", encoding="utf-8") as file:
    for line in file:
        print(line.strip())

strip() removes the newline at the end of each line.

Writing Multiple Lines

You can write strings one at a time.

lines = ["Asha\n", "Riya\n", "Kabir\n"]

with open("names.txt", "w", encoding="utf-8") as file:
    file.writelines(lines)

Remember that write() and writelines() do not automatically add newline characters.

Common Mistakes

A common mistake is using "w" when you mean "a". Write mode replaces the entire file. Append mode keeps existing content and adds new content at the end.

Another mistake is ignoring encoding. Using encoding="utf-8" makes text handling more predictable across systems.

A third mistake is assuming a missing file will be created in read mode. Mode "r" requires the file to already exist.

Quick Summary

• Use open() to work with files.
• Prefer with open(...) as file so files close automatically.
• "r" reads, "w" overwrites, and "a" appends.
• Use encoding="utf-8" for text files.
• read() reads the whole file.
• Looping over a file reads one line at a time.
• Add newline characters yourself when writing lines.

Practice Quiz

Now practice this topic with MCQs and explanations:

Start the Python File Handling quiz