Python Cheat Sheet: File Operations

1. Opening Files

f = open("file.txt", "r")        # Read mode (default)
f = open("file.txt", "w")        # Write mode (overwrites)
f = open("file.txt", "a")        # Append mode
f = open("file.txt", "rb")       # Read binary
f = open("file.txt", "r+", encoding="utf-8")  # Read/Write with encoding

2. Reading from Files

content = f.read()               # Read entire file
line = f.readline()             # Read one line
lines = f.readlines()           # Read all lines into a list

# Read line-by-line
for line in f:
    print(line.strip())

3. Writing to Files

f.write("Hello, world!")                     # Write a string
f.writelines(["Line 1\n", "Line 2\n"])       # Write a list of lines

4. File Context Management (with with)

with open("file.txt", "r") as f:
    content = f.read()
# File is automatically closed

5. File Modes Summary

• "r" – Read (default)
• "w" – Write (overwrite)
• "a" – Append
• "r+" – Read and write
• "b" – Binary mode (combine with others like "rb")
• "x" – Create a new file (error if it exists)

6. Checking File Existence

import os
if os.path.exists("file.txt"):
    print("File exists")

7. Deleting Files

import os
os.remove("file.txt")

8. Working with Directories

import os
os.mkdir("new_folder")              # Create a directory
os.rmdir("new_folder")             # Remove an empty directory
os.listdir(".")                    # List files in current directory
os.getcwd()                        # Get current working directory
os.chdir("/path/to/dir")           # Change directory

9. Handling File Exceptions

try:
    with open("file.txt", "r") as f:
        content = f.read()
except FileNotFoundError:
    print("File not found")
except IOError:
    print("IO error occurred")