Python Basics — Reading Files

Reading Files

Reading files is one of the first real-world tasks you’ll do in Python. Whether it’s log files, configuration, or data — the pattern is always the same.

The open() Function

file = open("example.txt", "r")   # "r" = read mode (default)
content = file.read()
print(content)
file.close()                       # Always close the file!

Better approach: Use with statement (covered later) to handle closing automatically.

File Modes for Reading

Mode	Description
"r"	Read text (default)
"rb"	Read binary (images, PDFs, etc.)

Reading Methods

Assume sample.txt contains:

Hello World
Python is great
File handling is easy

read() — Read Entire File

with open("sample.txt", "r") as f:
    content = f.read()
    print(content)
# Hello World
# Python is great
# File handling is easy

print(type(content))   # <class 'str'>
print(len(content))    # total characters including newlines

read(n) — Read n Characters

with open("sample.txt", "r") as f:
    first_five = f.read(5)
    print(first_five)   # Hello

    next_six = f.read(6)
    print(next_six)     #  World  (note the leading space)

readline() — Read One Line

with open("sample.txt", "r") as f:
    line1 = f.readline()
    print(line1)   # Hello World\n

    line2 = f.readline()
    print(line2)   # Python is great\n

readlines() — Read All Lines as a List

with open("sample.txt", "r") as f:
    lines = f.readlines()
    print(lines)
# ['Hello World\n', 'Python is great\n', 'File handling is easy\n']

# Strip newlines
clean_lines = [line.strip() for line in lines]
print(clean_lines)
# ['Hello World', 'Python is great', 'File handling is easy']

Iterating Line by Line (Best Practice)

For large files, iterate directly — this reads one line at a time and is memory-efficient:

with open("sample.txt", "r") as f:
    for line in f:
        print(line.strip())
# Hello World
# Python is great
# File handling is easy

This is the recommended approach for most file reading tasks.

File Encoding

Always specify encoding explicitly, especially on Windows:

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

# Read a file with different encoding
with open("legacy.txt", "r", encoding="latin-1") as f:
    content = f.read()

Tip: Always use encoding="utf-8" unless you know the file uses a different encoding.

File Paths

Relative Paths

# Relative to current working directory
with open("data/users.txt", "r") as f:
    content = f.read()

Absolute Paths

# macOS / Linux
with open("/home/user/data/users.txt", "r") as f:
    content = f.read()

# Windows (raw string to avoid escape characters)
with open(r"C:\Users\user\data\users.txt", "r") as f:
    content = f.read()

pathlib — Modern File Paths

from pathlib import Path

# Cross-platform path
file_path = Path("data") / "users.txt"

# Read the file
content = file_path.read_text(encoding="utf-8")
print(content)

# Check if file exists
if file_path.exists():
    print("File found!")

# Get file info
print(file_path.suffix)     # .txt
print(file_path.stem)       # users
print(file_path.parent)     # data
print(file_path.absolute()) # /full/path/to/data/users.txt

Handling FileNotFoundError

try:
    with open("nonexistent.txt", "r") as f:
        content = f.read()
except FileNotFoundError:
    print("File not found! Check the path.")

Or check first:

from pathlib import Path

file_path = Path("data.txt")
if file_path.exists():
    content = file_path.read_text()
else:
    print("File does not exist")

Summary

Method	Returns	Best For
read()	Entire file as string	Small files
read(n)	n characters	Peeking at file content
readline()	One line	Processing line by line
readlines()	List of all lines	When you need all lines in a list
for line in f:	One line per iteration	Large files (memory-efficient)

• Always specify encoding="utf-8" for text files
• Use pathlib.Path for modern, cross-platform file paths
• Handle FileNotFoundError for robust code
• Prefer iterating line by line for large files

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Next up: Writing Files →