Python | Joining only adjacent words in list

Sometimes, more than one type of data can come in Python list and sometimes it’s undesirably tokenized and hence we require to join the words that have been tokenized and leave the digits as they are. Let’s discuss certain ways in which this task can be achieved. Method #1 : Using list comprehension + “*” operator This task can be performed using the list comprehension, first by joining the words and then joining the digits and then separating only the numbers, while joining to form the resultant string. 

Python3

# Python3 code to demonstrate
# joining only adjacent words in list
# list comprehension + "*" operator

# initializing list
test_list = ['Geeks', '5', 'for', '9', 'Geeks' , '2', '5']

# printing original list
print("The original list : " + str(test_list))

# using list comprehension + "*" operator
# joining only adjacent words in list
res = [''.join([i for i in test_list if not i.isdigit()]),
                  *[j for j in test_list if j.isdigit()]]

# print result
print("The joined adjacent word list(ignoring digits) : " + str(res))

Time Complexity: O(n)
Space Complexity: O(n)

Output:

The original list : [‘Geeks’, ‘5’, ‘for’, ‘9’, ‘Geeks’, ‘2’, ‘5’] The joined adjacent word list(ignoring digits) : [‘GeeksforGeeks’, ‘5’, ‘9’, ‘2’, ‘5’]

Method #2 : Using itertools.chain.from_iterable() + groupby() + join() This task can also be performed using the groupby function which groups the digits together and then from_iterables function joins the list and characters together joined by the join function. 

Python3

# Python3 code to demonstrate
# joining only adjacent words in list
# itertools.chain.from_iterable() + groupby() + join()
from itertools import chain, groupby

# initializing list
test_list = ['Geeks', '5', 'for', 'Geeks' , '2', '3']

# printing original list
print("The original list : " + str(test_list))

# using itertools.chain.from_iterable() + groupby() + join()
# joining only adjacent words in list
num_group = groupby(test_list, key = str.isalpha)
both_group = [[''.join(i)] if j else list(i)
                      for j, i in num_group]

res = list(chain.from_iterable(both_group))

# print result
print("The joined adjacent word list(ignoring digits) : "
                                               + str(res))

Time Complexity: O(nlogn)
Space Complexity: O(n)

Output:

The original list : [‘Geeks’, ‘5’, ‘for’, ‘Geeks’, ‘2’, ‘3’] The joined adjacent word list(ignoring digits) : [‘Geeks’, ‘5’, ‘forGeeks’, ‘2’, ‘3’]