Python小技巧

Python小技巧

代码运行 jupyter notebook

快速构成一个字典序列

dict(zip('abcd',range(4)))
>>>{'a': 0, 'b': 1, 'c': 2, 'd': 3}

用类似三目运算输出

a =1
"11" if a==1 else "22"
>>>'11'

直接return 条件判断

def test(a):
    return "11" if a==1 else "22"

test(a)
>>>'11'

列表推导式生成字典

testlist = [(1,"a"),(2,"b"),(3,"c")]
{x[0]:x[1] for x in testlist}
>>>{1: 'a', 2: 'b', 3: 'c'}

{x:y for x in range(4) for y in range(10,14)}
>>>{0: 13, 1: 13, 2: 13, 3: 13}

使用heapq取最大值和最小值

import heapq
nums = [10,2,9,100,80]
heapq.nlargest(3,nums)
>>>[100, 80, 10]

heapq.nsmallest(3,nums)
>>>[2, 9, 10]

students = [
    {"name":"cc","score":100,"height":189},
    {"name":"bb","score":10,"height":169},
    {"name":"aa","score":80,"height":179}
           ]
heapq.nsmallest(2,students,key = lambda x:x["height"])
>>>[{'name': 'bb', 'score': 10, 'height': 169},
 {'name': 'aa', 'score': 80, 'height': 179}]

用lambda配合filter过滤

testlist = ['color', 'director_name', 'num_critic_for_reviews', 'duration',
           'director_facebook_likes', 'actor_3_facebook_likes', 'actor_2_name',
           'actor_1_facebook_likes', 'gross', 'genres', 'actor_1_name',
           'movie_title', 'num_voted_users', 'cast_total_facebook_likes',
           'actor_3_name', 'facenumber_in_poster', 'plot_keywords',
           'movie_imdb_link', 'num_user_for_reviews', 'language', 'country',
           'content_rating', 'budget', 'title_year', 'actor_2_facebook_likes',
           'imdb_score', 'aspect_ratio', 'movie_facebook_likes']
list(filter(lambda x:x.startswith('g'),testlist))
>>>['gross', 'genres']

用lambda配合正则过滤

import re
list(filter(lambda x:re.findall('^(g)',x),testlist))
>>>['gross', 'genres']

testlist = [
    {"name":"cc","score":100,"height":189},
    {"name":"bb","score":10,"height":169},
    {"name":"aa","score":80,"height":179}
           ]
list(filter(lambda x:"aa" in x.values(),testlist))
>>>[{'name': 'aa', 'score': 80, 'height': 179}]

列表降维

testlist = [1,[2,[3,4]]]
res = []

def fun(s):
    for i in s:
        if isinstance(i,list):
            fun(i)
        else :
            res.append(i)

fun(testlist)
res
>>>[1, 2, 3, 4]

funa = lambda L: sum(map(funa,L),[]) if isinstance(L,list) else [L]
funa(testlist)
>>>[1, 2, 3, 4]

funb = lambda x:[y for l in x for y in funb(l)] if type(x) is list else [x]
funb(testlist)
>>>[1, 2, 3, 4]

带条件的列表推导式

[x/2 for x in range(10) if x%2==0]
>>>[0.0, 1.0, 2.0, 3.0, 4.0]
[x for x in range(50) if x%5==0 and x%6==0]
>>>[0, 30]
[x+1 if x>=5 else x*10 for x in range(10)]
>>>[0, 10, 20, 30, 40, 6, 7, 8, 9, 10]
testlist = [[1,2,3],[4,5,6],[7,8]]
[y for x in testlist for y in x]
>>>[1, 2, 3, 4, 5, 6, 7, 8]

字典合并

dicta= {"name":"aa","score":80,"height":179}
dictb= {"language":"zh-CN"}

dict(dicta,**dictb)
>>>{'name': 'aa', 'score': 80, 'height': 179, 'language': 'zh-CN'}

dicta.update(dictb)
dicta
>>>{'name': 'aa', 'score': 80, 'height': 179, 'language': 'zh-CN'}