Walkthrough: sys.argv Greeter

例题: 命令行问候

≈ 8 min · python-cmdline · Open in WolfCode

The minimum viable CLI program. Take argv as a parameter so it's trivially testable.

Python · runnable

import sys

def greet(argv):
    if len(argv) < 1:
        return None
    name = argv[0]
    greeting = f"Hello, {name}!"
    if "--shout" in argv[1:]:
        greeting = greeting.upper()
    return greeting

def main(argv=None):
    if argv is None:
        argv = sys.argv[1:]
    msg = greet(argv)
    if msg is None:
        print("Usage: python greeter.py <name> [--shout]")
        sys.exit(1)
    print(msg)

# Demo (simulating various CLI invocations):
print(greet(["Ada"]))
print(greet(["Ada", "--shout"]))
print(greet([]))             # → None

Loading Python runtime (~5 MB, one-time)…

`sys.argv[1:]` — skip the script name

User typed	`sys.argv`	`sys.argv[1:]`
`python greeter.py Ada`	`["greeter.py", "Ada"]`	`["Ada"]`
`python greeter.py Ada --shout`	`["greeter.py", "Ada", "--shout"]`	`["Ada", "--shout"]`
`python greeter.py`	`["greeter.py"]`	`[]`

Walkthrough: sys.argv Greeter

sys.argv[1:] — skip the script name

`sys.argv[1:]` — skip the script name