W01 Python 使用技巧

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Lambda  #运算优先级最低 逻辑运算符: or 逻辑运算符: and 逻辑运算符:not 成员测试: in, not in 同一性测试: is, is not 比较: <,<=,>,>=,!=,== 按位或: | 按位异或: ^ 按位与: & 移位: << ,>> 加法与减法: + ,- 乘法、除法与取余: *, / ,% 正负号: +x,-x

#交换变量值

a,b = 5,10
print(a,b)      #5 10
a,b = b,a
print(a,b)      #10 5

#将列表中的所有元素组合成字符串

a = ['Python','is','awesome']
print(' '.join(a))      #Python is awesome

#查找列表中频率最高的值

a = [1,2,3,1,2,3,2,2,4,5,1]
print(max(set(a),key = a.count))        #2

#检查两个字符串是不是由相同字母不同顺序组成

from collections import Counter
str1 = '1234abcd'
str2 = '1243abcd'
print(Counter(str1) == Counter(str2))   #True

#反转字符串

a = 'abcdefghijklmnopqrstuvwxyz'
print(a[::-1])               #zyxwvutsrqponmlkjihgfedcba

for char in reversed(a):
    print(char,end='')      #zyxwvutsrqponmlkjihgfedcba

num = 123456789
print(int(str(num)[::-1]))  #987654321

#反转列表

a = [5,4,3,2,1]
print(a[::-1])              #[1, 2, 3, 4, 5]

for ele in reversed(a):
    print(ele,end='')       #12345

#转置二维数组

original = [['a','b'],['c','d'],['e','f']]
transposed = zip(*original)
print(list(transposed))     #[('a', 'c', 'e'), ('b', 'd', 'f')]

#链式比较

b = 6
print(4 < b < 7)            #True
print(1 == b < 20)          #False

#链式函数调用

def product(a,b):
    return a * b
def add(a,b):
    return a + b
b = True
print((product if b else add)(5,7))     #35
b = False
print((product if b else add)(5,7))     #12

#字典 get 方法

d = {'a':1,'b':2}
print(d.get('c',3))                     #3

#For Else

a = [1,2,3,4,5]
for el in a:
    if el == 0:
        break
else:
    print('did not break out of for loop')

#转换列表为逗号分割符格式

items = ['foo','bar','xyz']
print(','.join(items))                  #foo,bar,xyz

numbers = [2,3,5,10]
print((','.join(map(str,numbers))))     #2,3,5,10

data = [2,'hello',3,3.4]
print(','.join(map(str,data)))          #2,hello,3,3.4

#合并字典

d1 = {'a':1}
d2 = {'b':2}
print({**d1,**d2})                      #{'a': 1, 'b': 2}
print(dict(d1.items() | d2.items()))    #{'b': 2, 'a': 1}
d1.update(d2)
print(d1)                               #{'a': 1, 'b': 2}

#列表中最小和最大值的索引

lst = [40,10,20,30]
def minIndex(lst):
    return min(range(len(lst)),key=lst.__getitem__)
def maxIndex(lst):
    return max(range(len(lst)),key=lst.__getitem__)
print(minIndex(lst))        #1
print(maxIndex(lst))        #0

#移除列表中的重复元素

items = [2,2,3,3,1]
newitmes2 = list(set(items))
print(newitmes2)            #[1, 2, 3]

from collections import OrderedDict
items = ['foo','bar','bar','foo']
print(list(OrderedDict.fromkeys(items).keys()))     #['foo', 'bar']