Python程序代码阅读

1.beer.py

#!/usr/bin/env python3

"""
A Python version of the classic "bottles of beer on the wall" programming
example.
By Guido van Rossum, demystified after a version by Fredrik Lundh.
"""

import sys

n = 100
if sys.argv[1:]:	# 判断是否有传入数据，无，则n=100
    n = int(sys.argv[1])	# sys.argv[]用来存放外部输入的数据，sys.argv[0]表示代码名字（包含路径），sys.argv[1:]表示传入数据

def bottle(n):
    if n == 0: return "no more bottles of beer"
    if n == 1: return "one bottle of beer"
    return str(n) + "bottles of beer"

for i in range(n, 0, -1):
    print(bottle(i), "on the wall")
    print(bottle(i) + ".")
    print("Take one down, pass it around,")
    print(bottle(i-1), "on the wall.")

其中sys.argv的Python官方解释

sys.argv

The list of command line arguments passed to a Python script. argv[0] is the script name (it is operating system dependent whether this is a full pathname or not). If the command was executed using the -c command line option to the interpreter, argv[0] is set to the string '-c'. If no script name was passed to the Python interpreter, argv[0] is the empty string.

sys.argv[]用来存放外部输入的数据，sys.argv[0]表示代码名字（包含路径），sys.argv[1:]表示外部传入数据

比如你可以在命令行运行python beer.py 10，既可以使n=10

持续更新......