The study of List Comprehensions in Python(20170911)

the list comprehension is a generative which is uesd to make the list

example

print([x*x for x in range(1,10)]) # 1 4 9 16 25 36 49 64 81

it show 1*1 2*2 3*3…9*9

print([x*x for x in range(1,11)if x%2 == 1]) # 1 9 25 49 81

x == 2n+1, n == 0,1…10

print([m + n for m in ‘yuhan’ for n in ‘amu’])

the double list comprehension

import os
print(a for a in os.listdir(‘.’))

d = {‘a’:1,’b’:2,’c’:3}
for s,n in d.items():
print(s,n)

infor = [‘YUHANYU’]
print([s.lower() for s in infor]) # ‘yuhanyu’

the lower() function change the capital to lowcase

excersice

L1 = [‘Hello’,’World’,18,’Apple’,None]
print([s.lower() for s in L1 if isinstance(s,str) == True])

‘hello’,’world’,’apple’

must rightly use the forma