How to Convert a Float List to a String List in Python

The most Pythonic way to convert a list of floats fs to a list of strings is to use the one-liner fs = [str(x) for x in fs]. It iterates over all elements in the list fs using list comprehension and converts each list element x to a string value using the str(x) constructor.

This article shows you the simplest ways to convert a one-dimensional list consisting only of floats to a list of strings.

Problem: Given a list of floats [1.0, 2.0, 3.0]. How to convert it to a list of strings ["1.0", "2.0", "3.0"]?

Method 1: List Comprehension

Suppose we have a list:

a = [1.1, 1.2, 1.8, 0.5, 5.9, -2.3]

Now, check the type of the list:

print(type(a[0]))
# <class 'float'>

Let’s apply the built-in function str(), and get a list of strings using list comprehension:

print([str(a) for a in a])
# ['1.1', '1.2', '1.8', '0.5', '5.9', '-2.3']

💡 List comprehension is a compact way of creating lists. The simple formula is [expression + context]. Expression: What to do with each list element? Context: What elements to select? The context consists of an arbitrary number of for and if statements.

You can watch me explain list comprehensions in this video:

Check the type of numbers in the new list:

A = [str(a) for a in a]
print(type(A[0]))
# <class 'str'>

The built-in function str converts a float to a string representation of that float. Thus, it helps us create a new list of strings from the list of floats in a single line of code.

🌍 Recommended Tutorial: How to Convert a Float to a String in Python?

Method 2: Map Function

The built-in function map is well optimized and efficient; when it is called, the elements of the list are retrieved upon access. Therefore, one element is stored and processed in memory at a time, so the program doesn’t need to store the entire list of elements in the memory.

Apply to the same list a the following code:

a = [1.1, 1.2, 1.8, 0.5, 5.9, -2.3]
print(list(map(str, a)))
# ['1.1', '1.2', '1.8', '0.5', '5.9', '-2.3']

The map() function returns an iterable map object that we need to convert to a list using the built-in list() constructor.

Method 3: For Loop

Of course, you can also convert a list of floats to a list of strings using a simple for loop. This is what most people coming from a programming language such as Java and C++ would do as they don’t know the most Pythonic way of using list comprehension, yet (see Method 1).

a = [1.1, 1.2, 1.8, 0.5, 5.9, -2.3]
strings = []

for element in a:
    strings.append(str(element))

print(strings)
# ['1.1', '1.2', '1.8', '0.5', '5.9', '-2.3']

This basic method to convert a list of floats to a list of strings uses three steps:

• Create an empty list with strings = [].
• Iterate over each float element using a for loop such as for element in list.
• Convert the float to a string using str(element) and append it to the new string list using the list.append() method.

Method 4: String Formatting for Custom String Conversions

If this is not enough for you, for instance, you need a specific format of the converted strings such as only two digits after the decimal point, you should have a look at Python’s powerful string formatting capabilities.

For example, to convert a list of floats with many digits to a list of strings with only two digits, use the string.format() method:

a = [1.11111, 1.200023402, 1.844333, -0.5000001]
strings = ['{:.2f}'.format(x) for x in a]
print(strings)
# ['1.11', '1.20', '1.84', '-0.50']

💡 Python’s built-in format(value, spec) function transforms the input of one format into the output of another format as defined by you. Specifically, it applies the format specifier spec to the argument value and returns a formatted representation of value. For example, format(42, 'f') returns the string representation '42.000000'.

You can watch me introduce the formatting capabilities in this short guide:

Bonus Method 5: f-String

A more concise way to use Python’s formatting functionality can be accessed via f-strings in Python 3 and beyond. Convert a float list to a string list by using list comprehension and the float-to-string conversion expression f'{x:.2f}' on each list element x.

Here’s an example:

a = [1.11111, 1.200023402, 1.844333, -0.5000001]
strings = [f'{x:.2f}' for x in a]
print(strings)
# ['1.11', '1.20', '1.84', '-0.50']

Note you can increase or decrease the number of digits by setting the format specifier accordingly:

• f'{x:.2f}' yields two digits such as '3.12'
• f'{x:.3f}' yields two digits such as '3.123'
• f'{x:.4f}' yields two digits such as '3.1234'

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