Convert String float to float list in Python

Sometimes, while working with data, we could be dealing with numbers, that are in decimal and not integers. This is a general case in the data science domain. Let’s discuss how to resolve a problem in which we may have a comma-separated float number and we need to convert it to a float list.

Method #1 : Using list comprehension + split() + float()

A combination of the above methods can be used to perform this task. In this, we convert the String to a string list using split and then convert the string to float using float().

Python3

# Python3 code to demonstrate working of
# Convert String float to float list
# using list comprehension + split() + float()

# initializing string
test_str = "3.44, 7.8, 9.12, 100.2, 6.50"

# printing original string
print("The original string is : " + test_str)

# Convert String float to float list
# using list comprehension + split() + float()
res = [float(idx) for idx in test_str.split(', ')]

# printing result
print("The float list is : " + str(res))

Output : 

The original string is : 3.44, 7.8, 9.12, 100.2, 6.50
The float list is : [3.44, 7.8, 9.12, 100.2, 6.5]

Time complexity: O(n), where n is the length of the input string.

Auxiliary space complexity: O(n), where n is the length of the input string. 

Method #2 : Using map() + split() + float()

The combination of the above functions can also be used to solve this problem. In this, we perform the task of extending logic to the entire list using map(), the rest all the functionalities are performed as the above method.

Python3

# Python3 code to demonstrate working of
# Convert String float to float list
# using map() + split() + float()

# initializing string
test_str = "3.44, 7.8, 9.12, 100.2, 6.50"

# printing original string
print("The original string is : " + test_str)

# Convert String float to float list
# using map() + split() + float()
res = list(map(float, test_str.split(', ')))

# printing result
print("The float list is : " + str(res))

Output : 

The original string is : 3.44, 7.8, 9.12, 100.2, 6.50
The float list is : [3.44, 7.8, 9.12, 100.2, 6.5]

Time Complexity: O(N)
Auxiliary Space: O(N)

Method #3: Using ast.literal_eval()

The ast.literal_eval() function can also be used to convert a string of comma-separated float numbers to a float list. This function safely evaluates a string as a literal expression and returns the value.

Python3

import ast

# initializing string
test_str = "3.44, 7.8, 9.12, 100.2, 6.50"

# printing original string
print("The original string is : " + test_str)

# Convert String float to float list using ast.literal_eval()
res = ast.literal_eval("[" + test_str + "]")

# printing result
print("The float list is : " + str(res))
# this code is contributed by edula vinay kumar reddy

Output

The original string is : 3.44, 7.8, 9.12, 100.2, 6.50
The float list is : [3.44, 7.8, 9.12, 100.2, 6.5]

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

Method #4: Using for loop and append() method

Python3

# Python3 code to demonstrate working of
# Convert String float to float list
# using for loop and append()

# initializing string
test_str = "3.44, 7.8, 9.12, 100.2, 6.50"

# printing original string
print("The original string is : " + test_str)

# Convert String float to float list
# using for loop and append()
res = []
for elem in test_str.split(', '):
    res.append(float(elem))

# printing result
print("The float list is : " + str(res))

Output

The original string is : 3.44, 7.8, 9.12, 100.2, 6.50
The float list is : [3.44, 7.8, 9.12, 100.2, 6.5]

Time complexity: O(n), where n is the number of elements in the input string.
Auxiliary space: O(n), where n is the number of elements in the input string, as we need to store the float values in a list.