python - Python 的数字字典

Question

我是一名非常热爱编程的本科生。我在练习中遇到了一个问题，我不知道如何解决。

问题如下:

给定一个正整数列表，返回一个字典，其中包含数字 1-9 作为键，以该数字开头的数字作为值。注意:并非所有数字都可以使用

示例:

Input: [12, 34, 22, 24, 55, 67, 108, 999] 

Output: {1: [12, 108], 2: [22, 24], 3: [34], 5: [55], 6: [67], 9: [999] } 

示例 2:

Input: [10, 20, 30, 40] 

Output: {1: [10], 2: [20], 3: [30], 4: [40]}

我的回答是这样的:

def digit_dictionary(nums):
    num = nums.split(',')
    list_num = []
    for i in range(1,10):
        if i == nums[0]:
            list.update({i:nums[0]})
    return list_num

测试用例是这样的:

Traceback (most recent call last):
  File "/grade/run/test.py", line 12, in test_sparse_2
    self.assertEqual(digit_dictionary(n), a)
  File "/grade/run/bin/digit_dictionary.py", line 2, in digit_dictionary
    num = nums.split(',')
AttributeError: 'list' object has no attribute 'split

还有

Traceback (most recent call last):
  File "/grade/run/test.py", line 19, in test_sparse
    self.assertEqual(digit_dictionary(n), a)
  File "/grade/run/bin/digit_dictionary.py", line 2, in digit_dictionary
    num = nums.split(',')
AttributeError: 'list' object has no attribute 'split'

还有

Traceback (most recent call last):
  File "/grade/run/test.py", line 33, in test_full
    self.assertEqual(digit_dictionary(n), a)
  File "/grade/run/bin/digit_dictionary.py", line 2, in digit_dictionary
    num = nums.split(',')
AttributeError: 'list' object has no attribute 'split'

还有

Traceback (most recent call last):
  File "/grade/run/test.py", line 26, in test_empty
    self.assertEqual(digit_dictionary(n), a)
  File "/grade/run/bin/digit_dictionary.py", line 2, in digit_dictionary
    num = nums.split(',')
AttributeError: 'list' object has no attribute 'split'

我已经搜索过 Python 词典，但我仍然感到困惑。谢谢大家的帮助!

Answer 1

您可以对排序列表使用函数 gropby():

from itertools import groupby

l = [12, 34, 22, 24, 55, 67, 108, 999]

f = lambda x: int(str(x)[0])
l = sorted(l, key=f)
{k: list(g) for k, g in groupby(l, key=f)}
# {1: [12, 108], 2: [22, 24], 3: [34], 5: [55], 6: [67], 9: [999]}