Python：如何为列表的每个元素添加另一个列表中的每个元素？

Question

I'm really new to Python and I would like to manage some lists that I created. So, in list AI have the last two digits of years and in list BI have numbers from 000 to 999.

For each year in list A, I want to add every number in list BI guess using a loop...

listA = ['00', '01', '02', '03', '04', '05', '06', '07', '08', '09', '10', '11', '12', '13', '14', '15', '16', '17', '30', '31', '32', '33', '34', '35', '36', '37', '38', '39', '40', '41', '42', '43', '44', '45', '46', '47', '48', '49', '50', '51', '52', '53', '54', '55', '56', '57', '58', '59', '60', '61', '62', '63', '64', '65', '66', '67', '68', '69', '70', '71', '72', '73', '74', '75', '76', '77', '78', '79', '80', '81', '82', '83', '84', '85', '86', '87', '88', '89', '90', '91', '92', '93', '94', '95', '96', '97', '98', '99']

listB = ['000', '001', '002', '003', ...]

* somethingsomething loop *

listC = ['00000', '00001', '00002', ...]

Thank you!

Answer 1

Use itertools.product .

from itertools import product

listA = ['00', '01', '02', '03']
listB = ['000', '001', '002', '003']

listC = [a + b for a, b in product(listB, listA)] # ['00000', '00001', '00002', ...]

The product function iterates through the Cartesian product of the supplied iterables (the k-tuples of all combinations drawing one from each list). String concatenation is used to join the elements of the tuple ( a + b ). The list comprehension puts them all into a big ol' list.

Answer 2

While itertools.product is handy, a simple nested comprehension will do just as fine:

list_a = ['00', '01', '02', '03']  # Python conventions call for snake_case
list_b = ['000', '001', '002', '003']

list_c = [b + a for b in list_b for a in list_a]
# ['00000', '00001', '00002', '00003', ... ]

Note here that the first for has the wider scope, which sometimes seems counter-intuitive compared to natural English.

Answer 3

You will need to iterate over listB , so you would do:

for itemB in listB:

And then for each of these items, you will need to match it with every element in listA , so you would do another nested loop over listA .

for itemA in listA:

And then inside both loops, you would have all combinations of itemA and itemB . So you will just need to concatenate them and add them to an output list.

Full Solution

ouptut = []
for itemB in listB:
  for itemA in listA:
    output.append(itemB + itemA)

itertools.product as mentioned in another solution, could give you a more concise solution, since it replaces the two for loops.

Answer 4

> Code to reproduce listA

listA = []
for i in range(0,10):
    for j in range(0,10):
        e = str(i)+str(j)
        listA.append(e)
print(listA)

> Code to reproduce listB


listB = []
for i in range(0,10):
    for j in range(0,10):
        for k in range(0,10):
            e = str(i)+str(j)+str(k)
            listB.append(e)
print(listB)

> Now we just iterate over each element of listA and append one by one each element of listB, and keep appending the result to listC to get the final output list



listC = []
for i in listA:
    for j in listB:

        listC.append(i+j)
print(listC)

Answer 5

You can use the inbuild function zip()

For example:

class SumList():

    def __init__(self, this_list):
        self.mylist = this_list

    def __add__(self, other):
        new_list = [ x + y for x,y in zip(self.mylist, other.mylist)]
        return SumList(new_list)

    def __repr__(self):
        return str(self.mylist)

cc = SumList([1,2,3,4])
dd = SumList([100,200,300,400])    
ee = cc + dd
print(ee)