python的HelloWorld

#  !/usr/bin/python
#  同一行写多条语句，用;隔开
import sys; x1 = 'runoob'; sys.stdout.write(x1 + '\n')

# import和from...import
# 若from sys import argv,path;后面的语句变为print('\n python 路径为',path)不需再写出sys
for i in sys.argv:
    print(i)
print('\n python 路径为', sys.path)

# print默认换行输出
print("Hello World")
print("你好，世界")
# print不换行
print("xx", end="")
print(" ", end='')
print("yy", end="")
print('')

# 注释的三种写法---------------
# 1.第一个注释
'''
  2.这是多行注释
'''
"""
  3.这也是多行注释
"""
# python使用缩进而不是大括号{}
if True:
    print("对了")
else:
    print("错了")
# print("报错") 这样写，由于缩进不一致，报错


# 变量赋值
a1 = b1 = c1 = 1
a2, b2, c2 = 1, 2.0, "runoob"

# 字符串的3中写法
word = '这是字符串1'
sentence = "这是字符串2"
paragraph = """
    这是字符串3==================================================== 
    """
# 等待用户输入如下。按下回车键后退出
input()


# isinstance和type
class A:
    pass


class B(A):
    pass


isinstance(A(), A); print(isinstance(A(), A))  # returns True print()
type(A()) == A;  print(type(A()) == A)  # returns True
isinstance(B(), A);  print(isinstance(B(), A))  # returns True
type(B()) == A;  print(type(B()) == A)  # returns False

# 帮助信息
help(max)
print(max.__doc__)