在python列表中对连续的类似项进行分组

Question

I have a list containing different data types, say numbers and strings:

foo = [5,2,'a',8,4,'b','y',9, 'd','e','g']

Let's say I want to find all consecutive strings in the the list, and group them together:

bar = [ ['a'],['b','y'],['d','e','g'] ]

How can I do this

Answer 1

This is a wonderful opportunity to use groupby :

from itertools import groupby


foo = [5,2,'a',8,4,'b','y',9, 'd','e','g']
bar = [list(g) for k, g in groupby(foo, key=lambda x: isinstance(x, str)) if k]

which produces the desired:

[['a'], ['b', 'y'], ['d', 'e', 'g']]

Answer 2

Iterate through each element in the list, if it is of type str , append it to one_d_array , otherwise, append one_d_array to two_d_array , provided one_d_array is not empty. Reset one_d_array whenever the element is not of type str

lst = [5,2,'a',8,4,'b','y',9, 'd','e','g', 3]
ind = 0
two_d_arr = []
one_d_arr = []
while(ind < len(lst)):
    cur_element = lst[ind]
    if(isinstance(cur_element, str) == True):
        one_d_arr.append(cur_element)
    else:
        if(len(one_d_arr) != 0):
            two_d_arr.append(one_d_arr)
        one_d_arr = []
    ind = ind+1
if(len(one_d_arr) != 0):
            two_d_arr.append(one_d_arr)
print(two_d_arr)

Answer 3

Without using any import, you can do it through a good old "for loop" iterating over the elements of the lists. Here is a code working also for any type you want, not only string:

def group_list(a_list, a_type):
    res = []
    sublist = []
    for elem in a_list:
        if isinstance(elem, a_type):
            # Here the element is of  type a_type: append it to a sublist
            sublist.append(elem)
        else:
            # Here the element is not of type a_type: append the sublist (if not empty) to the result list
            if sublist:
                res.append(sublist)
                sublist = []
    # If the last element of the list is of type a_type, the last sublist has not been appended: append it now
    if sublist:
        res.append(sublist)

    return res


foo = [5,2,'a',8,4,'b','y',9, 'd','e','g']
print(group_list(foo,str)) 
# [['a'], ['b', 'y'], ['d', 'e', 'g']]