创建一个 function 以列表作为参数并仅保留大于 5 的数字

Question

I am trying to create a function that takes a list as an argument and keeps only the numbers that are greater than 5 by creating a new empty list inside the function and only append it with numbers that are greater than five, looping over the given one. However, append does not return anything or it returns None.

lst = [[0, 1, 5, 6, 9], [5, 5, 5, 5], [42, 1337], [-100, 100]]

def more_than_five(lst):
  result = []
  for i in range(len(lst)):
    if i > 5:
      result.append(i)
  return result


Output should be (individually. not as one list):

[6,9]
[]
[42, 1337]
[100]

Answer 1

You can use a double comprehension to iterate over a list of lists:

def more_than_five(lst):
    return [[i for i in l if i > 5] for l in lst]
print(more_than_five(lst))

# Output
[[6, 9], [], [42, 1337], [100]]

Without a comprehension:

def more_than_five(lst):
    result = []
    for j, l in enumerate(lst):
        result.append([])
        for i in l:
            if i > 5:
                result[j].append(i)
    return result
print(more_than_five(lst))

# Output
[[6, 9], [], [42, 1337], [100]]

Update : If your function only processes one list at a time:

def more_than_five(lst):
    return [i for i in lst if i > 5]

print(more_than_five(lst[0]))
print(more_than_five(lst[1]))
# and so on

Or:

def more_than_five(lst):
    result = []
    for i in lst:
        if i > 5:
            result.append(i)
    return result

print(more_than_five(lst[0]))
print(more_than_five(lst[1]))
# and so on

Output:

[6, 9]
[]
[42, 1337]
[100]