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Core Python › 4 of 14

Functions & Lambdas

Arguments, defaults, *args/**kwargs, and closures.

python
def train(model, data, *, lr=1e-3, epochs=10, **kwargs):
    """Keyword-only args after * prevent mistakes."""
    print(lr, epochs, kwargs)

train(m, d, lr=3e-4, scheduler="cosine")

sorted(runs, key=lambda r: r["val_loss"])
Tip: Never use a mutable default like def f(x=[]) — use None and create inside.

⚡ Quick check

  • ✓ *args tuple, **kwargs dict
  • ✓ * forces keyword-only
  • ✓ lambda for small key funcs