python的一些语法糖

# 1."else" after the "while","for":
# the "else" object will be executed when no "break" was executed in "while","for" object before
# num = [1, 2, 3, 4]
# mark = 0
# while mark < len(num):
# n = num[mark]
# if n % 2 == 0:
# print(n)
# # break
# mark += 1
# else:
# print("done")

# 2."zip" to zip two lists
# a = [1, 2, 3]
# b = ['one', 'two', 'three']
# list(zip(a, b))

# 3.推导式

# 3.1.列表推导式：[ expr for value in collection if condition ]
# strings = ['Bob', 'Tom', 'alice', 'Jerry', 'Wendy', 'Smith']
# result = [name.upper() for name in strings if len(name) > 3]

# 3.2.字典推导式：{ key_exp : value_exp for expression in iterable }
# strings = ['import', 'is', 'with', 'if', 'file', 'exception']
# result = {key: val for val, key in enumerate(strings)}

# 3.3.集合推导式：{ expression for expression in iterable }
# strings = ['a', 'is', 'with', 'if', 'file', 'exception']
# result = {len(s) for s in strings}

# 4.函数

# 4.1.默认参数值
# 需要同时设定所有参数的默认值，不能单独设定部分参数，
# 否则会报错：SyntaxError: non-default argument follows default argument
# 同时列表字典等可变数据类型不能作为默认参数值
# def do(a=1, b=1, c=1):
# print(a, b, c)
#
#
# do()
# do(3)
# do(3, 3)
# do(3, 3, 3)

# 4.2.lambda匿名函数
# do = lambda x: x * x
# print(do(4))

# 5.super()调用父类方法
# class Father():
# def __init__(self, name):
# self.name = name
# print("Father is here")
#
#
# class Son(Father):
# def __init__(self, name, age):
# super().__init__(name)
# self.age = age
#
#
# a = Son('Jack', 15)
# print(a.name, a.age)
#
#
# 6.实例方法：
# 实例方法，以self作为第一个参数，当它被调用时，Python会把调用该方法的的对象作为self参数传入。
# class Person():
# age = 15
#
# def __init__(self, Age):
# self.age = Age
# print(Person.age) # Person.age为类特征
# print(self.age) # self.age为对象特征
#
#
# Jack = Person(20)

# 7.{} & ".format"
# usually used to change the format of output
# print('{} {} {}'.format(11, 22, 33))
# print('{2:2d} {0:-10d} {1:10d}'.format(11, 22, 33))
# print('{a} {b} {c}'.format(a=11, b=22, c=33))