如何在 Python 中通过 itertools 函数使用索引

问题描述

我有一个包含多个列表的列表，它看起来像这样：

import itertools

stand_city = 11
stand_liverpool = 6.5

premier_league = [
             ['A1','Manchester City','10,1','Aguero'],['A2','11,2','Mahrez'],['A3','13,5','Sterling'],['B1','Liverpool','4,'Mane'],['B2','5,6','Salah'],['B3','7,'Jota']]

现在对于每个列表，我想在它超过 stand_city 或 stand_liverpool 之前获得最后一个值。取决于列表中的 index[1]。如果是 Manchester City 我需要它使用 stand_city，如果 Liverpool 我希望它使用 stand_liverpool。我希望将这些值存储在新列表中。

这是我的代码：

new_list  = []
for key,sublists in itertools.groupby(premier_league,lambda y:y[0]):
    club = (list(sublists)[0][1])
    if club == 'Manchester City':
        v=[] 
        for v in itertools.takewhile(lambda x:float(x[-2].replace(",","."))<stand_city,sublists):
            pass
        if v: 
            x = v[-1]
            new_list.append(x)
    elif club == 'Liverpool':
        v=[] 
        for v in itertools.takewhile(lambda x:float(x[-2].replace(","."))<stand_liverpool,sublists):
            pass
        if v: 
            x = v[-2]
            new_list.append(x)
            
print(new_list) 

这是我的输出：

[]

这是我想要的输出：

10,1
5,6

解决方法

我对您的代码做了一些小的修改以获得您想要的结果。

stand_city = 11
stand_liverpool = 6.5

premier_league = [
             ['A1','Manchester City','10,1','Aguero'],['A2','11,2','Mahrez'],['A3','13,5','Sterling'],['B1','Liverpool','4,'Mane'],['B2','5,6','Salah'],['B3','7,'Jota']]

res = []
for g,value in groupby(premier_league,key = lambda x:x[1]): # group by according to index 1
    less_than = [] # temporary list to hold all values less than your threshold for a particular group
    for i in value: # iterate thorugh the values in each group
        float_i = float(i[2].replace(',','.')) # convert index 2 to float
        to_compare = stand_city if g == 'Manchester City' else stand_liverpool
        if float_i < to_compare: # compare `float_i` with either `stand_city` or `stand_liverpool` based on group
            less_than.append(i[2]) # add all values that meet the condition to a temp list
    res.extend(less_than[-1:]) # take only the last element from the list for each group,`[-1:]` is done to prevent cases where `less_than` is an empty list
print(res) # ['10,6']

或者更短的方式

from itertools import groupby
res = []
for g,key = lambda x:x[1]):
    last = [x[2] for x in value if float(x[2].replace(','.')) <= (stand_city if g == 'Manchester City' else stand_liverpool)][-1:]
    res.extend(last)

print(res) # ['10,6']

修复了 OP 的代码以使其正常工作

import itertools

new_list  = []
for key,sublists in itertools.groupby(premier_league,lambda y:y[1]):
    if key == 'Manchester City':
        v=[] 
        for v in itertools.takewhile(lambda x:float(x[-2].replace(",","."))<stand_city,sublists):
            pass
        if v: 
            x = v[-2]
            new_list.append(x)
    elif key == 'Liverpool':
        v=[] 
        for v in itertools.takewhile(lambda x:float(x[-2].replace(","."))<stand_liverpool,sublists):
            pass
        if v: 
            x = v[-2]
            new_list.append(x)
            
print(new_list)