a = 1
b = '2'
try:
print('运算开始')
print(a + b)
except Exception as e:
print('运行报错')
print(e)
else:
print('未出现异常')
finally:
print('运行完毕')
列表 []:无类型限制
元组 ():无类型限制,不可修改
集合 {}:无序,自动排序
字典 {}:{}的默认类型
_list = [10, 20, 3, 8, 11]
_list.sort()
print(_list)
_list.sort(reverse=True) #降序
print(_list)
_list = ['a', 'hello', '1', 2, 'b']
try:
_list.sort()
print(_list)
except Exception as e:
print('出现异常')
print(e)
_list = ['hello', 'world', 'nihao', 'a', 'c', 'b']
print(_list)
_list.reverse() # 逆置
print(_list)
_list.clear() # clear可用于清空列表/元组/集合/字典
print(_list)
_list = [1, 2, 3]
_list *= 3
print(_list)
# 元组也可进行乘法,不过会进行重构
# 1 2 3 4 这四个数字可以组成多少个各个位数不同的数字
count = 0
_list = [1, 2, 3, 4]
for i in _list:
for j in _list:
for k in _list:
for l in _list:
if len({i, j, k, l}) == 4:
sum = i * 1000 + j * 100 + k * 10 + l
print(sum, end=' ')
count += 1
print(f'\ncount = {count}')
x = 'python'
y = iter(x)
print(y)
print(next(y, '已经迭代结束了'))
print(next(y, '已经迭代结束了'))
print(next(y, '已经迭代结束了'))
print(next(y, '已经迭代结束了'))
print(next(y, '已经迭代结束了'))
print(next(y, '已经迭代结束了'))
print(next(y, '已经迭代结束了')) #防报错
print(next(y, '已经迭代结束了'))
print(next(y, '已经迭代结束了'))
# 拆包
i, j, k, l = [1, 2, 3, 4]
print(i, end=" ")
print(j, end=" ")
print(k, end=" ")
print(l)
# 聚合, 短板效应
x = [1, 2]
y = [1, 2, 3]
z = ['hello', 'world', '!']
print(zip(x, y, z))
for e in zip(x, y, z):
print(e)
# 映射
x = [2, 3, 10]
y = [5, 2, 2]
a = map(pow, x, y) # pow()幂函数,pow(2, 5), pow(3, 2), pow(10, 2)
for e in a:
print(e)
filter()函数:筛选出符合某个函数的数据
函数会根据 提供的函数对指定的可迭代对象的每个元素进行遍历
将遍历的运算结果为真的元素,以迭代器的形式返回
def Even(n):
return n % 2 == 0
a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
b = list(filter(Even, a))
print(b) # [2, 4, 6, 8, 10]
import random
a = random.randint(1, 100) # 生成[1, 100)之间的随机整数
b = random.uniform(1, 100) # 生成[1, 100)之间的随机浮点数
print(a, b)
def func():
name = 'python'
def inner():
print('hello world')
return name
return inner
f = func()
f() # hello world
print(f())
# hello world
# python
lambda是匿名函数关键字
func = lambda x, y : x + y
print(func(2, 5)) # 7
func = lambda x : x if x % 2 == 0 else None
print(func(4)) # 4
print(func(5)) # None
闭包:本质也是函数,参数和返回值都是函数,对函数进行增强
语法糖:没有增加新功能,对语言没影响,更方便程序员使用
import time
def CountTimeWrapper(func):
#闭包
def ImproveFunc(*args, **kwargs): # 增强函数应该把接收到的参数传给原函数
start_time = time.perf_counter()
ret = func(*args, **kwargs) # 传入参数并记录返回值
end_time = time.perf_counter()
print(f'函数的执行时间为{end_time - start_time}')
return ret
return ImproveFunc
@CountTimeWrapper # @闭包函数名,就是装饰器,自增强一次
def PrintOdds(lim=100):
cnt = 0
for i in range(lim):
if i % 2 == 0:
cnt += 1
return cnt
if __name__ == '__main__':
# PrintOdds = CountTimeWrapper(PrintOdds)
# 装饰器等价于在第一次调用时执行上面语句
print(PrintOdds())