Python Day-List 理解-练习

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列表理解

当您想要基于现有列表的值创建新列表时,列表理解提供了更短的语法。 (参考-https://www.w3schools.com/python/python_lists_comprehension.asp)

示例:1
方法:1

fruits = ["apple", "banana", "cherry", "kiwi", "mango"] newlist = []  for x in fruits:   if "a" in x:     newlist.append(x)  print(newlist) 

方法:2(综合)

fruits = ["apple", "banana", "cherry", "kiwi", "mango"]  newlist = [x for x in fruits if "a" in x] print(newlist) 

输出:

['apple', 'banana', 'mango'] 

示例:2

l = [10,20,30,40] newlist = [] #using normal loop for num in l:     newlist.append(num**2) print(newlist)  #using loop in comprehensive way newlist = [num**2 for num in l] print(newlist) 

输出:

[100, 400, 900, 1600] [100, 400, 900, 1600] 

练习:
1.从2个列表中查找相似的数字以及从相同的2个列表中查找不同的数字。
l1 = [10,20,30,40]
l2 = [30,40,50,60]
得到这个输出:
a) 30,40

#30,40 l1 = [10,20,30,40] l2 = [30,40,50,60] #normal method  for num in l1:     for no in l2:         if num== no:             print(num,end=' ') #comprehensive  print([num for num in l1 for no in l2 if num==no]) 

输出:

[30, 40] 

b) 10,20,50,60

l1 = [10,20,30,40] l2 = [30,40,50,60] #comprehensive output = [num for num in l1 if num not in l2]  output = output + [num for num in l2 if num not in l1] print(output)  #normal method for num in l1:     if num not in l2:         print(num,end=' ')  for num in l2:     if num not in l1:         print(num,end=' ') 

输出:

[10, 20, 50, 60] 10 20 50 60  

2。以综合方法查找给定输出的程序
l1 = [1,2,3]
l2 = [5,6,7]
输出:[(1, 5), (1, 6), (1, 7), (2, 5), (2, 6), (2, 7), (3, 5), (3, 6) , (3, 7)]

l1 = [1,2,3] l2 = [5,6,7]  l = [(i,j) for i in l1 for j in l2 if i!=j] print(l) 

输出:

[(1, 5), (1, 6), (1, 7), (2, 5), (2, 6), (2, 7), (3, 5), (3, 6), (3, 7)] 

3。查找给定输出的程序:
s = "a1b2c3"
输出:abc123

方法:1

s = "a1b2c3"  alpha_list = [] num_list = []  for letter in s:     if letter.isalpha():         alpha_list.append(letter)     else:         num_list.append(letter)  print("".join(alpha_list+num_list)) 

方法:2

s = "a1b2c3" letter=''.join([i for i in s if i.isalpha()]) no=''.join([i for i in s if i.isdigit()])  print(letter+no) 

输出:

abc123 

4。查找给定输出的程序:

s = "a4k3b2"
输出:aeknbd

s = "a4k3b2" i = 0  while i<len(s):     first = s[i]     second = int(s[i+1])     print(first, chr(ord(first)+second),sep='',end='')     i+=2 

输出:

aeknbd

说明:

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-->使用ord(first)获取first的ascii值,然后将其添加到其中以查找新字符。
-->ord() 用于查找 ascii 值。
-->hr() 转换 ascii 值-->character.

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