python學習筆記——列表解析，字典解析，集合解析篩選元素

1 / 過濾掉列表中的負數

方式1：

from random import randint
data = [1,5,-3,-6,8,0,9]
list = []
for x in data:
    if x >=0:
        list.append(x)
print(list)
[1, 5, 8, 0, 9]

方式二 （filter()函數）

from random import randint
data = [randint(-10,10) for _ in range(10)]
data
Out[9]: 
[7, 3, -4, 4, 10, -2, 6, 1, 1, -6]
filter(lambda x:x>=0 ,data)
Out[10]: 
<filter at 0x1c5eb204a58>

lambda 是匿名函數

方式三 ——列表解析

data
Out[18]: 
[7, 3, -4, 4, 10, -2, 6, 1, 1, -6]
[x for x in data if x>=0]
Out[19]: 
[7, 3, 4, 10, 6, 1, 1]

2 / dict 篩選出某些元素  ——字典解析

dict = {x : randint(60,100) for x in range(1,21)}
dict
Out[21]: 
{1: 92,
 2: 85,
 3: 100,
 4: 91,
 5: 78,
 6: 62,
 7: 80,
 8: 83,
 9: 71,
 10: 73,
 11: 73,
 12: 74,
 13: 74,
 14: 84,
 15: 87,
 16: 68,
 17: 70,
 18: 70,
 19: 85,
 20: 67}

{k: v for k,v in dict.items() if v >90}
Out[24]: 
{1: 92, 3: 100, 4: 91}

3 / 集合解析

data
Out[25]: 
[7, 3, -4, 4, 10, -2, 6, 1, 1, -6]
s = set(data)
s
Out[27]: 
{-6, -4, -2, 1, 3, 4, 6, 7, 10}
{ x for x in s if x%3==0}
Out[28]: 
{-6, 3, 6}