如何从一个列表中返回2个单独的列表？

Question

If have this list here:

[25, 8, 22, 9] 

How can I make the program create 2 seperate lists, and print them both? One should contain all the numbers less than 20, and the other needs to contain all the numbers greater than 20. The final print result should be displayed like this: [8, 9] , [25, 22]

Answer 1

>>> predicates = lambda x:x<20, lambda x:x>20
>>> print [filter(pred, [25, 8, 22, 9]) for pred in predicates]
[[8, 9], [25, 22]]

Answer 2

Use list comprehensions :

>>> L = [25, 8, 22, 9]
>>> [x for x in L if x < 20]
[8, 9]
>>> [x for x in L if x > 20]
[25, 22]

Answer 3

a =  [25, 8, 22, 9] 
print [x for x in a if x > 20]
print [x for x in a if x < 20]

You use here list comprehensions . List comprehension looks like:

[ f(x) for x in a if cond(x) ]

That means: produce me a list that consists of f(x) for each element of x for that cond(x) is True .

In our case f(x) is simply x . And cond(x) is x > 20 or x < 20 (please note also that if you have 20s in your list, they will disappear from the result).

If it is a homework you can solve the task in more low-level way:

a = [25, 8, 22, 9]
list1 = []
list2 = []
for elem in a:
  if elem > 20:
     list1.append(elem)
  if elem < 20:
     list2.append(elem)
print list1
print list2

Here you iterate through the list and check its elements. That elements that are greater than 20 you append to one list; and that that are lesser thatn 20 — to the other.

Answer 4

Note: the assumes you want twenty in listTwo

listOne = [x for x in yourList if x < 20]
listTwo = [x for x in yourList if x >= 20]

print listOne
print listTwo

Although you should use list comprehensions you might be interested in the for loop approach if you are starting with python

listOne = []
listOne = []

for x in yourList:
    if x < 20:
        listOne.append(x)
    else:
        listTwo.append(x)

Answer 5

def print_split_list(raw_list, split_value):
    lower_list = [v for v in raw_list if v < split_value]
    upper_list = [v for v in raw_list if v >= split_value]
    print lower_list, upper_list

print_split_list([25, 8, 22, 9], 20)  # => [8, 9] [25, 22]

Answer 6

li = [25, 8, 22, 9]
li.sort()

for i, x in enumerate(li):
    if x > 20:
        print li[:i]
        print li[i:]
        break