How Python Reads a File

The idea

You have a file on your computer. Python needs to find it, open it, and read what's inside.

Three methods. One pattern. All the same with open() block.

Where to put your file

Python looks for files relative to where your script is located.

The simplest setup: put the file in the same folder as your .py script.

project/
    script.py
    soldiers.txt

Then you open it like this:

with open("soldiers.txt", "r") as f:
    ...

If the file is in a subfolder:

with open("data/soldiers.txt", "r") as f:
    ...

If Python can't find the file, you get a FileNotFoundError. That almost always means the path is wrong — check the folder, check the filename, check the extension.

The file for this lesson

Download soldiers.txt and place it in the same folder as your script before running any of the examples below.

read() — the whole file at once

with open("soldiers.txt", "r") as f:
    content = f.read()
print(content)

Returns the entire file as one string — newlines included.

Good for small files. Not ideal for large ones — the whole thing loads into memory at once.

readlines() — all lines as a list

with open("soldiers.txt", "r") as f:
    lines = f.readlines()
print(lines)

Output → ['Raven\n', 'Wolf\n', 'Ghost\n', 'Viper\n', 'Bull\n']

Each line becomes an element. The \n at the end is the newline character — strip it when you need clean values:

with open("soldiers.txt", "r") as f:
    lines = [line.strip() for line in f.readlines()]
print(lines)

Output → ['Raven', 'Wolf', 'Ghost', 'Viper', 'Bull']

readline() — one line at a time

with open("soldiers.txt", "r") as f:
    first  = f.readline()
    second = f.readline()
print(first.strip())
print(second.strip())

Each call moves to the next line. Useful when you only need the first few lines of a large file.

Looping directly over the file — most common

with open("soldiers.txt", "r") as f:
    for line in f:
        print(line.strip())

Output:

Raven
Wolf
Ghost
Viper
Bull

Python reads the file line by line without loading it all into memory. This is the pattern you'll use most.

Handling a missing file

If the file might not exist, wrap it in a try/except:

try:
    with open("soldiers.txt", "r") as f:
        for line in f:
            print(line.strip())
except FileNotFoundError:
    print("File not found. Check the path.")

Heads up!

• Always use encoding="utf-8" if your file contains special characters
• readlines() keeps the \n — use .strip() to clean it
• read() on a large file loads everything into memory at once — use a loop instead
• The file path is relative to where you run the script — not where the script file is saved

What you should understand now

• Put the file in the same folder as your script for the simplest setup
• read() returns the whole file as a string
• readlines() returns all lines as a list — with \n included
• readline() reads one line at a time
• Looping directly over the file is the most memory-efficient pattern
• Use try/except FileNotFoundError when the file might not exist