Python | Joining unicode list elements

Sometimes we can receive data in different formats other than the conventional list or strings or integers or characters. Python has many other data types and knowledge of handling them is usually useful. This article demonstrates the joining of Unicode characters in the list. Let’s discuss certain ways in which this can be done. 

Method #1 : Using join() + list comprehension

In this method, we first convert the unicode elements of strings to the string elements and then perform the join operation to get the joined resultant string from unicode elements list. Works in Python2 only. 

Python3

# Python code to demonstrate
# Joining unicode list elements
# using join() + list comprehension

# Initializing list
test_list = ['We', 'love', 'Geeksforgeeks']
map(unicode, test_list)

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

# Join unicode list elements
# using join() + list comprehension to
res = b':'.join(str(i) for i in test_list)

# Printing the result
print("The joined string is : " + res)

Output : 

The original list is : ['We', 'love', 'Geeksforgeeks']
The joined string is : We:love:Geeksforgeeks

Method #2: Using join() + str()

The list comprehension can be avoided as the join function implicitly takes the joins of all the list elements and returns the joined unicodes which can then be converted to string using str function. Works in Python2 only. 

Python3

# Python3 code to demonstrate
# Joining unicode list elements
# using join() + str()

# initializing list
test_list = ['We', 'love', 'Geeksforgeeks']
map(unicode, test_list)

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

# Join unicode list elements
# using join() + str()
res = str(u':'.join(test_list))

# printing result
print("The joined string is : " + res)

Output : 

The original list is : ['We', 'love', 'Geeksforgeeks']
The joined string is : We:love:Geeksforgeeks

Method#3: using separator

Using a for loop to iterate through the list and concatenate the strings with a separator.

Algorithm:

1. Initialize a list lst and a separator sep.
2. Initialize a variable joined_str with the first element of lst.
3. Loop through the remaining elements of lst.
4. Concatenate the separator and the current element of lst to joined_str.
5. Print the final joined_str variable.

Python3

lst = ['We', 'love', 'Geeksforgeeks']

sep = ':'
joined_str = lst[0]

for i in range(1, len(lst)):
    joined_str += sep + lst[i]
print(joined_str)

Output

We:love:Geeksforgeeks

Time Complexity: O(n), where n is the length of the list.
Auxiliary Space: O(n), where n is the length of the list.

Method 4:Using the reduce() function

The above code joins the elements of a list of strings using the reduce() function from the functools module. It defines a custom function to concatenate two elements with a colon and then uses reduce() to apply this function to all elements of the list, resulting in a single joined string.

Algorithm:

1. Import the functools module
2. Define the original list of strings
3. Define a custom function to concatenate two elements with a colon
4. Use the reduce() function to apply the custom function to all elements of the list, resulting in a single joined string
5. Print the result.

Python3

# Import the functools module
import functools

# Define the original list
original_list = ['We', 'love', 'Geeksforgeeks']

# Define the function to concatenate two elements with a colon
def concat_with_colon(x, y):

    return x + ":" + y

# Use the reduce() function to concatenate all elements
joined_string = functools.reduce(concat_with_colon, original_list)

# Print the result
print(joined_string)

Output

We:love:Geeksforgeeks

Time complexity: O(n)
Auxiliary space: O(n)

Method 5:Using defaultdict method

The approach using defaultdict and join() has a time complexity of O(n), where n is the number of elements in the input list. This is because we need to iterate over the entire list once to populate the defaultdict, and then we need to iterate over the keys of the defaultdict to join them with the separator.

Algorithm Steps:

1. Import the defaultdict class from the collections module.
2. Define the input list my_list.
3. Create an empty defaultdict joined_dict with a list as the default value.
4. Iterate over each element in my_list, and append the element to joined_dict using the element as both the key and the value.
5. Join the keys of joined_dict with the separator ‘:’ using the join() method and store the result in joined_string.
6. Print the joined_string

Python3

from collections import defaultdict

# Input list
my_list = ['We', 'love', 'Geeksforgeeks']

# Creating a defaultdict with a list as the default value
joined_dict = defaultdict(list)

# Iterating over the list and append
# each element to the defaultdict
for element in my_list:
    joined_dict[element].append(element)

# Join the elements in the defaultdict
# with ':' separator using join()
joined_string = ':'.join(joined_dict.keys())

# Printing the joined string as answer
print(joined_string)

Output

We:love:Geeksforgeeks

Time complexity: O(n)
Auxiliary space: O(n)