Convert List to Delimiter Separated String - Python

The task of converting a list to a delimiter-separated string in Python involves iterating through the list and joining its elements using a specified delimiter. For example, given a list a = [7, "Gfg", 8, "is", "best", 9] and a delimiter "*", the goal is to produce a single string where each element is converted to a string and separated by "*", resulting in "7*Gfg*8*is*best*9".

Using str.join()

str.join() is the most efficient way to convert a list into a delimiter-separated string. It works by first converting each element into a string and then joining them using the specified delimiter. This method is highly optimized for performance and is the preferred choice in most cases.

a = [7, "Gfg", 8, "is", "best", 9]  
delim = "*"

res = delim.join(map(str, a))
print(res)

7*Gfg*8*is*best*9

Explanation: map(str, a) converts each element of a into a string since integers cannot be directly joined and delim.join(...) joins all converted string elements using * as a separator.

Using list comprehension

List comprehension allows transforming each element into a string before joining them, making it useful when additional modifications are needed. While slightly less efficient than map(str, a), it remains a clean and readable alternative to str.join().

a = [7, "Gfg", 8, "is", "best", 9]  

res = "*".join([str(ele) for ele in a])
print(res)

7*Gfg*8*is*best*9

Explanation: [str(ele) for ele in a] converts each element of a into a string, and "*".join(...) joins all converted elements using * as a separator, creating a single formatted string.

Using reduce()

reduce() from the functools module applies a binary function iteratively to combine all elements into a single string. Though functional in nature, it is less efficient than str.join() due to repeated string creation.

from functools import reduce
a = [7, "Gfg", 8, "is", "best", 9]  

res = reduce(lambda x, y: str(x) + "*" + str(y), a)
print(res)

7*Gfg*8*is*best*9

Explanation: reduce() applies the lambda function cumulatively to the list elements, where lambda x, y: str(x) + "*" + str(y) converts x and y to strings, concatenates them with * as a separator and continues this process until all elements are merged into a single string.

Using for loop

A traditional for loop can manually concatenate elements into a string. Although simple and intuitive, this approach is inefficient due to repeated immutable string operations, making it slower for large lists.

a = [7, "Gfg", 8, "is", "best", 9]  
res = ""

for ele in a:
    res += str(ele) + "*"
res = res[:-1]
print(res)

7*Gfg*8*is*best*9

Explanation: for loop converts each element to a string, appends it to res with * and res[:-1] removes the trailing * for proper formatting.