Print and Input

Python · Reference cheat sheet

📋 Overview

print writes to stdout; input reads a line from stdin as str. Fine for CLIs and debugging; prefer logging for applications and argparse for structured CLIs.

🔧 Core concepts

print converts with str(). Soft space separation via sep. Use f-strings for formatting.

💡 Examples

print options:

print("a", "b", "c", sep="-")
print("loading", end="...", flush=True)
print(" done")

import sys
print("error!", file=sys.stderr)

input and parse:

name = input("Name: ").strip()
raw = input("Count: ").strip()
try:
    count = int(raw)
except ValueError:
    print("Not an integer", file=sys.stderr)
    raise SystemExit(1)
print(f"Hello {name} x{count}")

EOF-safe loop:

import sys

def main() -> None:
    for line in sys.stdin:
        text = line.strip()
        if not text:
            continue
        print(text.upper())

if __name__ == "__main__":
    main()

Pretty debug:

from pprint import pprint

data = {"users": [{"id": 1, "name": "Ada"}], "ok": True}
pprint(data, width=40)

⚠️ Pitfalls

• input always returns str — cast explicitly.
• EOF (Ctrl+D / Ctrl+Z) raises EOFError on input().
• Password prompts: use getpass.getpass so input is not echoed.
• Leaving debug prints in libraries pollutes consumer output — use logging.
• Locale/encoding issues on redirected pipes — prefer UTF-8 aware environments.

🔗 Related

• F-strings
• Argparse
• Logging
• Examples: cli tool
• Strings
• Exceptions