如何将元组列表更改为单个列表？

Question

i have the following lists which consists of tuples, every tuple has items related together the items in every tuple represents an animal, his speed and his weight respictivly

tuples_list=[(cat,250,50),(lion,650,400),(tiger,700,450)]

firstly i wanted to arrange the tuple_list in a descinding manner according to the second item in the tuples so i used the following

def sorted_tuple(tuples_list):
    return(sorted(tuple_lists, key = lambda x: x[1], reverse=True))#to sort the tuples inside the list from highest to lowest speed

so the tuples_list became:

tuples_list=[(tiger,700,450),(lion,650,400),(cat,250,50)]

now i need to do the following separate the animals into a list, their speed into a second list and their weight into a third list so i did the following

animal=[]
speed=[]
weight=[]
animal,speed,weight=zip(*sorted_tuple(tuples_list))

so i expected the following result

animal=[tiger,lion,cat]
speed= [700,  650, 250]
weight=[450,  400,  50]

so every animal has his speed and weight directly below him in the other lists but when i tried to change an item in the speed list into another value under certain condition

lets say speed[0]=speed[0]+50

i got the following error

'tuple' object does not support item assignment

so where is the problem exactly please correct me regards

Answer 1

OP: where is the problem exactly please correct me

When you tried to convert the list of tuples into list of list using:

animal,speed,weight=zip(*sorted_tuple(tuples_list))

it did not create list of list rather only tuples ie:

speed= (700,  650, 250)

You can still add the speed in the tuple using:

speed[0]+50

But you cannot change their value since tuples in Python are immutable , so you cannot do this:

speed[0]=speed[0]+50

Use the index on sorted list of tuples and then assign the animal, speed and weight:

def sorted_tuple(tuples_list):
    return(sorted(tuples_list, key = lambda x: x[1], reverse=True))

tuples_list=[('tiger',700,450),('lion',650,400),('cat',250,50)]    
temp_lst = sorted_tuple(tuples_list)

animal = [x[0] for x in temp_lst]
speed =  [x[1] for x in temp_lst]
weight = [x[2] for x in temp_lst]

print(speed[0]+ 50)

EDIT :

You could also achieve the same using zip() with indexing:

animal  = list(list(zip(*temp_lst))[0])
speed = list(list(zip(*temp_lst))[1])
weight = list(list(zip(*temp_lst))[2])
print(speed[0]+ 50)

Answer 2

don't use zip function, if preferences are fixed then you can directly iterate within that list, Here it is,

tuples_list=[('tiger',700,450),('lion',650,400),('cat',250,50)]

animal = [i[0] for i in tuples_list]
speed = [i[1] for i in tuples_list]
weight= [i[2] for i in tuples_list]

speed[0]=speed[0]+50

output

['tiger', 'lion', 'cat']
[750, 650, 250]
[450, 400, 50]