argparse Defaults

argparse 默认值

≈ 20 min · python-cmdline · Open in WolfCode

type= converts strings for you. default= fills in when the flag isn't given. Two changes that turn a toy parser into a real one.

Python · runnable

import argparse

def parse_args(argv):
    parser = argparse.ArgumentParser(description="Echo a message N times.")
    parser.add_argument("message")
    parser.add_argument("--count", type=int, default=1)
    parser.add_argument("--upper", action="store_true")
    return parser.parse_args(argv)

a = parse_args(["hello"])
print(a.message, a.count, a.upper)              # hello 1 False

a = parse_args(["hi", "--count", "3"])
print(a.message, a.count, a.upper, type(a.count).__name__)
# hi 3 False int    ← a.count is an INT, not the string "3"

a = parse_args(["wow", "--count", "5", "--upper"])
print(a.message, a.count, a.upper)              # wow 5 True

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What action / type / default each does

Pattern	Behavior
`action="store_true"`	Boolean — True if present, False otherwise. No value follows.
`type=int`	argparse calls `int(value)` for you.
`default=1`	What `args.count` is when `--count` isn't passed.