sort函数，lambda函数，filter函数，for_else循环控制
1. sort()
L.sort(key)对L使用key规则进行排序，返回None值，使用时不要assign一个list = .sort()
from random import randrange
L = [randrange(20) for _ in range(10)]
L.sort()
L
>>>
[0, 2, 5, 6, 7, 7, 16, 18, 19, 19]
#key的默认是从小到大排序
2.sorted()
sorted(L)对L进行排序，返回排序后的list
from random import randrange
L = [randrange(20) for _ in range(10)]
L = sorted(L)
L
>>>
[6, 7, 7, 11, 11, 11, 13, 13, 13, 17]
3.lambda
lambda简化了def function的书写方法，lambda 函数输入值: 函数body。
f = lambda : 3
f()
>>>
3
#含义是定义一个无输入值的函数，返回数字3
f = lambda x: 3
print(f(4), f(2))
>>>
3 3
#含义是定义一个输入值为x的函数，无论x是多少，返回值都是3
4.order排序
对于order，默认排序规则是先比较第一个数字，再比较第二个数字。
L = [(randrange(20), randrange(20)) for _ in range(10)]
L.sort()
print(list(L))
>>>
[(2, 11), (2, 14), (3, 6), (6, 10), (7, 8), (10, 3), (12, 14), (13, 7), (14, 9), (17, 10)]
5.制定复杂排序规则
（1）以order两数之和的大小进行排序
L = [(randrange(20), randrange(20)) for _ in range(10)]
def f(x):
return x[0] + x[1]
L.sort(key = f)
print(list(L))
>>>
[(9, 0), (5, 8), (12, 3), (16, 7), (14, 12), (15, 12), (18, 12), (17, 14), (14, 19), (18, 16)]
（2）借助lambda函数简化程序
L = [(randrange(20), randrange(20)) for _ in range(10)]
L.sort(key = lambda x: x[0] + x[1])
print(list(L))
（3）以绝对值大小进行排序
L = [randrange(-19, 20) for _ in range(10)]
L.sort(key = abs)
print(list(L))
>>>
[1, 1, 2, 4, -4, -5, 5, -6, 9, 13]
（4）偶数在前奇数在后
L = [randrange(20) for _ in range(20)]
L.sort(key = lambda x: x % 2)
print(list(L))
>>>
[16, 2, 2, 4, 14, 12, 0, 14, 10, 6, 9, 9, 17, 11, 15, 17, 15, 11, 15, 7]
（5）偶数在前奇数在后，且按大小顺序输出
L = [randrange(20) for _ in range(20)]
L.sort(key = lambda x: (x % 2, x))
print(list(L))
>>>
[0, 0, 0, 0, 2, 4, 12, 14, 16, 18, 18, 3, 3, 7, 11, 13, 13, 15, 15, 17]
如果排序有多种要求，可以借助上文提到的order方法多次限定实现
6. filter()
filter(规则，object)根据规则筛选符合条件的object。
（1）筛选质数
from math import sqrt
L = [randrange(100) for _ in range(30)]
def is_prime(x):
if x < 2:
return False
for d in range(2, round(sqrt(x)) + 1):
if x % d == 0:
return False
return True
L_filter = list(filter(is_prime, L))
L_filter.sort()
L_filter
>>>
[13, 17, 79, 89, 97]
（2）筛选偶数
L = [randrange(100) for _ in range(30)]
set(filter(lambda x: not x % 2, L))
>>>
{6, 12, 24, 34, 42, 50, 64, 68, 70, 78, 80, 82, 98}
7. for else
如果for循环全部完成，则执行else后语句，否则跳过
from random import randrange
for _ in range(7):
generated_number = randrange(-10, 60)
print(f'Generated number: {generated_number}')
if generated_number < 0:
continue
if generated_number >= 50:
break
print('\tUnless it is a single digit, will determine what it is equal to modulo 4')
if generated_number < 10:
pass
elif generated_number % 4 == 1:
print('\tEqual to one modulo four')
elif generated_number % 4 == 2:
print('\tEqual to two modulo four')
elif generated_number % 4 == 3:
print('\tEqual to three modulo four')
else:
print('\tDivisible by four')
else:
print('No number greater than 49 has been generated')
>>>
Generated number: 22
Unless it is a single digit, will determine what it is equal to modulo 4
Equal to two modulo four
Generated number: 46
Unless it is a single digit, will determine what it is equal to modulo 4
Equal to two modulo four
Generated number: 40
Unless it is a single digit, will determine what it is equal to modulo 4
Divisible by four
Generated number: 50
>>>
Generated number: 27
Unless it is a single digit, will determine what it is equal to modulo 4
Equal to three modulo four
Generated number: 35
Unless it is a single digit, will determine what it is equal to modulo 4
Equal to three modulo four
Generated number: 4
Unless it is a single digit, will determine what it is equal to modulo 4
Generated number: -4
Generated number: 2
Unless it is a single digit, will determine what it is equal to modulo 4
Generated number: 3
Unless it is a single digit, will determine what it is equal to modulo 4
Generated number: 29
Unless it is a single digit, will determine what it is equal to modulo 4
Equal to one modulo four
No number greater than 49 has been generated
