python逼格提升

1.合并可以匹配的条件

s1 = 7
if s1 > 5 and s1 < 10:
    print(s1)


s1 = 7
if 5 < s1 < 10:
    print(s1)

2.if条件避免与布尔值比较

l1 = []
if l1 != []:
    print('l1 is not empty')
else:
    print('l1 is empty')

    
l1 = []
if l1:
    print('l1 is not empty')
else:
    print('l1 is empty')

此时等价于if True，属于False的值：None、False、数字0、空列表元组字典集合，但是有的时候数字0我们是有用的，所以我们用is来比较

s1 = 0
if s1:
    print('s1 is not empty')
else:
    print('s1 is empty')

    
s2 = 0
if s2 is not None:
    print('s2 is not empty')
else:
    print('s2 is empty')

so，我们可以看出is与==的意义是不同的，事情的真相是is比较的是内存地址，None在python是单例的，==比较的是值

l1 = [0, 1, 2]
l2 = [0, 1, 2]
if l1 is l2:
    print('l1 is l2')
else:
    print('l1 is not l2')

if l1 == l2:
    print('l1 == l2')
else:
    print('l1 != l2')

3.简单的if else用三元运算代替

if 1 == 2:
    s1 = '北方姆Q'
else:
    s1 = 'bfmq'


s1 = '北方姆Q' if 1 == 2 else 'bfmq'

4.enumerate迭代器，可以循环的对象可以使用，返回两个值，第一个是位置，第二个是对应元素

l1 = ['dfmq', 'xfmq', 'nfmq', 'bfmq']
for index, value in enumerate(l1):
    print('%d %s' % (index, value))

5.for+else表示当循环完for内所有后才会执行else下的程序，中途break则不会

l1 = [11, 22, 33, 44]

for s1 in l1:
    if s1 <= 100:
        break
else:
    print('喵喵喵喵!')

6.少定义布尔返回值变量

def low1(a, b, c):
    flag = False
    if a == b == c:
        flag = True
    return flag

ret = low1(6, 6, 6)


def low2(a, b, c):
    if a == b == c:  
        return True
    else:
        return False

ret = low2(6, 6, 6)


def f1(a, b, c):
    return a == b == c

ret = f1(6, 6, 5)

7.被调用事不要抛出自定义异常

def get_json_url(url):
    try:
        url = json.load(url)
        return url

    except Exception as e:
        print('something wrong!')
        return None

这样第三方只会获得一个something wrong!信息，无法确定哪里出了错误，so
def get_json_url(url):
　　return json.load(url)
这样异常会返回给调用者

8.多用EAFP，少用LBYL

def get(user):
    if user is None:
        print('no user!')
    print(user.info)
LBYL在进行程序前需要考虑前提条件是否成立，因此穿插了很多条件检查


def get(user):
    try:
        print(user.info)

    except NameError:
        print('no user!')

9.连等号赋同值

a = 10
b = 10
c = 10


a = b = c = 10
此时a=666，但是b跟c是不会变的哦~

10.python支持直接调换值哦

10.python支持直接调换值哦
a = 10
b = 100
temp = a
a = b
b = temp


a = 10
b = 100
a, b = b, a

11.多次调用对象方法时，可以用链式调用方法，避免中间产生过多变量及内存

s1 = '  north is good!'
s2 = s1.strip()
s3 = s2.upper()
s4 = s3.replace('!', '?')


s2 = s1.strip().upper().replace('!', '?')
当然过多了连续调用可能会影响到可读性，so，简短的调用可以写在一起，出现一个比较大变化时另起一行是比较好的

12.使用isinstance对不同类型参数进行对应操作

def get_size(some_object):
    if isinstance(some_object, (list, dict, str, tuple, set)):
        return len(some_object)
    elif isinstance(some_object, (bool, type(None))):
        return 1
    elif isinstance(some_object, (int, float)):
        return int(some_object)


print(get_size('bfmq'))
print(get_size([1, 2, 3, 4, 5]))
print(get_size(10.0))
print(get_size([]))

 13.使用product精简多层嵌套循环

from itertools import product

x_list = ['a', 'b', 'c']
y_list = ['d', 'e', 'f']
z_list = [1, 2, 3]

for x in x_list:
    for y in y_list:
        for z in z_list:
            print(f"{x}:{y}:{z}")


for x, y, z in product(x_list,y_list, z_list):
    print(f"{x}:{y}:{z}")

14.使用any/all进行判断

i_list = [x for x in range(10)]

for i in i_list:
    if i > 5:
        print(True)
        break


if any(i > 5 for i in i_list):
    print(True)