Default Args Greeting

默认参数与关键字参数

≈ 20 min · python-functions · Open in WolfCode

Parameters can have default values. Callers can skip them — or override only the ones they care about, using keyword arguments.

Defaults make optional parameters

Python · runnable

def greet(name, greeting="Hello", punctuation="!"):
    return f"{greeting}, {name}{punctuation}"

print(greet("Ada"))
print(greet("Ada", "Welcome"))
print(greet("Ada", "Hi", "?"))
print(greet("Ada", greeting="Good morning"))
print(greet("Ada", punctuation="."))    # ← skip middle!

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

Keyword arguments — the killer feature

greet("Ada", punctuation=".") leaves greeting at its default "Hello" but overrides the third parameter. Without keyword args you'd have to write greet("Ada", "Hello", ".") — forcing you to remember the default.

When to use defaults

Frequently-used good values — port=8080, timeout=30
Backwards compatibility — adding a parameter with a default doesn't break existing callers
Optional flags — def fetch(url, retry=False):