将内部 0 和 1 索引附加到第二索引二维列表列表中的所有元素 - python

Question

Hello new to python here... wondering what the best way is to solve a problem like this.

I have a 2d array that look something like this:

a = [['October 17', 'Manhattan', '10024, 10025, 10026'], 
     ['October 17', 'Queen', '11360, 11362, 11365, 11368']]

Would like to iterate over this to create a new list or data frame that looks like the following:

10024, October 17, Manhattan
10025, October 17, Manhattan
10026, October 17, Manhattan
11360, October 17, Queens
11362, October 17, Queens
11365, October 17, Queens
11368, October 17, Queens

Any insight would be greatly appreciated.

Thank you.

Answer 1

You may need to iterate over the values, and for each iterate over the several indices you have

values = [['October 17', 'Manhattan', '10024, 10025, 10026'],
          ['October 17', 'Queens', '11360, 11362, 11365, 11368']]

result = [[int(idx), row[0], row[1]]
          for row in values
          for idx in row[2].split(',')]
df = DataFrame(result, columns=['idx', 'date', 'place'])

To obtain

[[10024, 'October 17', 'Manhattan'], [10025, 'October 17', 'Manhattan'], 
 [10026, 'October 17', 'Manhattan'], [11360, 'October 17', 'Queens'], 
 [11362, 'October 17', 'Queens'], [11365, 'October 17', 'Queens'], 
 [11368, 'October 17', 'Queens']]


     idx        date      place
0  10024  October 17  Manhattan
1  10025  October 17  Manhattan
2  10026  October 17  Manhattan
3  11360  October 17     Queens
4  11362  October 17     Queens
5  11365  October 17     Queens
6  11368  October 17     Queens

Answer 2

Azro's answer is great, but here's a way to solve this problem that is more explicit (if you're truly new to Python, this approach might be more clear so you can understand what is happening — it doesn't rely on nested list comprehension.)

a = [['October 17', 'Manhattan', '10024, 10025, 10026'], 
['October 17', 'Queen', '11360, 11362, 11365, 11368']]

# initialize an empty list to put our reformatted data into
final_result = []

for inner_list in a:
    # get the first two items
    first_item = inner_list[0]
    second_item = inner_list[1]

    # split the third list item, and remove trailing and leading whitespace
    remaining_data = [x.strip() for x in inner_list[2].split(',')]

    # iterate over the remaining data
    for item in remaining_data:
        # first, create a new sublist containing our first two items
        new_entry = [item, first_item, second_item]

        # add our new_entry into the final result list
        final_result.append(new_entry)

print(final_result)