交换两个变量

# a = 4 b = 5
a,b = b,a
# print(a,b) >> 5,4

多个变量赋值

a,b,c = 4,5.5, Hello 
#print(a,b,c) >> 4,5.5,hello

将列表中的多个值分配给变量

a,b,*c = [1,2,3,4,5]
print(a,b,c)
> 1 2 [3,4,5]

列表中偶数的和(使用列表索引和sum函数)

a = [1,2,3,4,5,6]
s = sum([num for num in a if num%2 == 0])
print(s)
>> 12

从列表中删除多个元素

#### Deleting all even
a = [1,2,3,4,5]
del a[1::2]
print(a)

>[1, 3, 5]

读取文件

lst = [line.strip() for line in open( data.txt )]
print(lst)

通过使用列表功能,使得代码更简单,更短

list(open( data.txt ))

##Using with will also close the file after use
with open("data.txt") as f:
    lst=[line.strip() for line in f]
print(lst)

将数据写入文件

with open("data.txt", a ,newline= ) as f: 
    f.write("you are awsome")

创建列表

lst = [i for i in range(0,10)]
print(lst)
> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

###############################################

lst = list(range(0,10))
print(lst)

使用相同的方法创建一个字符串列表

lst = [("Hello "+i) for i in [ Karl , Abhay , Zen ]]
print(lst)
> [ Hello Karl ,  Hello Abhay ,  Hello Zen ]

映射列表或类型转换整个列表

list(map(int,[ 1 , 2 , 3 ]))
> [1, 2, 3]

list(map(float,[1,2,3]))
> [1.0, 2.0, 3.0]

[float(i) for i in [1,2,3]]
> [1.0, 2.0, 3.0]

创建集合

### Square of all even numbers in an range
{x**2 for x in range(10) if x%2==0}

> {0, 4, 16, 36, 64}

Fizz Buzz(编写一个程序来打印从1到20的数字。但如果是3的倍数,打印Fizz,如果是5的倍数,打印Buzz,如果同时是3和5的倍数,打印FizzBuzz,否则打印数字)

[ FizzBuzz  if i%3==0 and i%5==0
    else  Fizz  if i%3==0 
    else  Buzz  if i%5==0 
    else i  for i in range(1,20)]

回文

text =  level 
ispalindrome = text == text[::-1]
ispalindrome

> True

用空格分隔的整数到一个列表

lis = list(map(int, input().split()))
print(lis)

> 1 2 3 4 5 6 7 8
[1, 2, 3, 4, 5, 6, 7, 8]

Lambda函数

# Function that returns square of any number
sqr = lambda x: x * x
sqr(10)

> 100

打印图案

n = 5
print( .join( 😀  * i for i in range(1, n + 1)))

>
😀
😀😀
😀😀😀
😀😀😀😀
😀😀😀😀😀  

查找阶乘

import math
n = 6
math.factorial(n)

> 720

斐波纳契数列(一组数字,其中每个数字(斐波那契数)是前面两个数字的和)

fibo = [0,1]
[fibo.append(fibo[-2]+fibo[-1]) for i in range(5)]
fibo

> [0, 1, 1, 2, 3, 5, 8]  

质数(质数是一个只能被自身和1整除的数)

list(filter(lambda x:all(x % y != 0 for y in range(2, x)), range(2, 13)))

> [2, 3, 5, 7, 11]  

查找最大数值

findmax = lambda x,y: x if x > y else y 
findmax(5,14)

> 14

or 
max(5,14)  

线性代数(将列表中的元素缩放2到5倍)

def scale(lst, x):
    return [i*x for i in lst] 


scale([2,3,4], 2)

> [4,6,8]  

矩阵转置

a=[[1,2,3],
   [4,5,6],
   [7,8,9]] 
transpose = [list(i) for i in zip(*a)] 
transpose

> [[1, 4, 7], [2, 5, 8], [3, 6, 9]]

计数(某个值在文本中出现的次数)

import re

len(re.findall( python , python is a programming language. python is python. ))

> 3

用其他文本替换文本

"python is a programming language.python is python".replace("python", Java )

> Java is a programming language. Java is Java

模拟抛硬币(从一组给定的选择中生成一些随机选择)

mport random

random.choice([ "zheng" ,"fan"])

> zheng

生成组(对)

groups = [(a, b) for a in [ a ,  b ] for b in [1, 2, 3]] 
groups

> [( a , 1), ( a , 2), ( a , 3), ( b , 1), ( b , 2), ( b , 3)]

 

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