Python - Convert List of Integers to a List of Strings

We are given a list of integers and our task is to convert each integer into its string representation. For example, if we have a list like [1, 2, 3] then the output should be ['1', '2', '3']. In Python, there are multiple ways to do this efficiently, some of them are: using functions like map(), reduce() or even list comprehensions. Let's explore these methods to better understand this.

Using map()

map() function applies a given function (in this case, str) to every item in the list and returns a map object, which we convert to a list.

a = [1, 2, 3, 4, 5]

# Convert each element to string using map
b = list(map(str, a))

print(b)

['1', '2', '3', '4', '5']

Explanation:

• map(str, a) applies the str function to every item in list a.
• The result is a map object, which we convert to a list using list().
• This is one of the most efficient and readable ways to convert types in bulk.

Using List Comprehension

List comprehension is a concise way to create a new list by applying an expression to each item in an existing list. We use a list comprehension to loop through each element in the list a.

a = [1, 2, 3, 4, 5]

# Convert each element using a list comprehension
b = [str(x) for x in a]

print(b)

['1', '2', '3', '4', '5']

Explanation:

• This loops through each element x in the list a and applies str(x).
• The result is collected into a new list.

Using for Loop

We can also convert the list of integers into strings by using a simple for loop. In this method, we create an empty list b. We then loop through each element x in list a, convert it to a string using str(), and append it to the list b.

a = [1, 2, 3, 4, 5]

b = []
for x in a:
    b.append(str(x)) # Convert each number to string and append to b
    
print(b)

['1', '2', '3', '4', '5']

Explanation:

• We start with an empty list b.
• For each element x in a, we convert it using str(x) and append it to b.

Using reduce() from functools

reduce() function from the functools module can also be used, although it’s a bit more complex than the previous methods. It reduces a list into a single value using a function, which can be used to build a list in this case.

from functools import reduce
a = [1, 2, 3, 4, 5]

# Using reduce to accumulate the list of strings
b = reduce(lambda acc, x: acc + [str(x)], a, [])

print(b)

['1', '2', '3', '4', '5']

Explanation:

• reduce() applies the lambda function to accumulate a result.
• It starts with an empty list [] and adds str(x) for each element.