Python File Handling Cheat Sheet

with open("data.txt", "r") as f:   # 'r' read (default)    contents = f.read()# file is automatically closed here, even on exception# common modes:# 'r'  read (default)      'w'  write, truncates existing file# 'a'  append               'x'  create, fails if file exists# 'rb' read binary          'r+' read and write

with open("data.txt") as f:    contents = f.read()      # entire file as one stringwith open("data.txt") as f:    lines = f.readlines()     # list of lines, keeps '\n'with open("data.txt") as f:    for line in f:              # memory-efficient, one line at a time        print(line.strip())

with open("out.txt", "w") as f:    f.write("Hello\n")    f.writelines(["line1\n", "line2\n"])with open("out.txt", "a") as f:    f.write("appended line\n")   # adds without erasing existing content

from pathlib import Pathp = Path("data") / "file.txt"   # cross-platform path joiningp.exists()p.is_file()p.read_text()p.write_text("content")list(Path(".").glob("*.py"))     # all .py files in current dir

import csvwith open("data.csv", newline="") as f:    reader = csv.DictReader(f)    for row in reader:        print(row)import jsonwith open("data.json") as f:    data = json.load(f)with open("out.json", "w") as f:    json.dump(data, f, indent=2)