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)