Python | Ways to convert array of strings to array of floats

Sometimes in a competitive coding environment, we get input in some other datatypes and we need to convert them into other forms this problem is the same as when we have an input in the form of string and we need to convert it into floats. Let’s discuss a few ways to convert an array of strings in Python to an array of floats.

Input: ['1.1' '1.5' '2.7' '8.9']
Output: [ 1.1  1.5  2.7  8.9]
Explanation: In This, we are converting an array of strings to an array of floats.

Convert Array of Strings to Array of Float in Python

We can convert Python String Array to Float using different methods.

• Using for loop and float() function
• Using List Comprehension
• Using map() function
• Using astype
• Using Numpy
• Using np.fromstring
• Using np.asarray()
• Using np.asfarray

Convert String Array to Array Float using for loop and float() function

Here is the approach to convert an array of strings from Python to an array float using loop and float functions. Create an empty array to store the converted floats. Loop through each element of the input array and convert the current element to a float using the float() function. Append the converted float to the output array. Return the output array. Below is the implementation of the above approach.

Python3

def convert_strings_to_floats(input_array):
    output_array = []
    for element in input_array:
        converted_float = float(element)
        output_array.append(converted_float)
    return output_array
input_array = ['1.1', '1.5', '2.7', '8.9']
output_array = convert_strings_to_floats(input_array)
print(output_array)

Output

[1.1, 1.5, 2.7, 8.9]

Time Complexity: O(n), where n is the length of the input array.
Auxiliary Space: O(n), since we are creating a new array to store the converted floats.

Convert String Array to Array Float using List Comprehension

Here is the approach to convert an array of strings from Python to an array float using list comprehension. List comprehension provides a concise way to convert an array of strings to an array of floats.

Python3

string_array = ["5.55", "6.66", "7.77"]
float_array = [float(string) for string in string_array]

print(float_array)

Output

[5.55, 6.66, 7.77]

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

Convert String Array to Array Float using Map

Here is the approach to convert an array of strings from Python to an array float using the map() function. We have used the map() function to apply the float() function to each element in the input list. It Returns the resulting iterator as a list using the list() function. Here is the implementation of this approach.

Python3

def convert_to_floats(arr):
    # Use the map function to apply the float function to each element in the input list
    result = map(float, arr)
    # Return the resulting iterator as a list
    return list(result)

# Test the function
arr = ['1.1', '1.5', '2.7', '8.9']
print(convert_to_floats(arr))

Output

[1.1, 1.5, 2.7, 8.9]

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

Python String to float using Astype

Here is the approach to convert an array of strings from Python to an array float using astype(). It is used to change the datatype of a series. if a  column could be imported as a string but to do operations we have to convert it into a float, astype() is used to do such data type conversions.

Python3

import numpy as np

ini_array = np.array(["1.1", "1.5", "2.7", "8.9"])

# printing initial array
print ("initial array", str(ini_array))

# converting to array of floats
# using np.astype
res = ini_array.astype(np.float)

print ("final array", str(res))

Output

initial array ['1.1' '1.5' '2.7' '8.9']
final array [ 1.1  1.5  2.7  8.9]

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

Convert an Array of Strings to an Array of Floats in Numpy

Convert Python String Array to Array Float using np.fromstring 

Here is the approach to convert the array of strings from Python to an array float using np.fromstring(). The Numpy.fromstring() function creates a new one-dimensional array initialized from text data in a string.

Python3

import numpy as np

ini_array = np.array(["1.1", "1.5", "2.7", "8.9"])

# printing initial array
print ("initial array", str(ini_array))

# converting to array of floats
# using np.fromstring
ini_array = ', '.join(ini_array)
ini_array = np.fromstring(ini_array, dtype = np.float,
                                           sep =', ' )
print ("final array", str(ini_array))

Output

initial array ['1.1' '1.5' '2.7' '8.9']
final array [ 1.1  1.5  2.7  8.9]

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

Convert Python String Array to Array Float using np.asarray()

Here is the approach to convert an array of strings from Python to an array float using np.asarray(). The numpy.asarray()function is used when we want to convert the input to an array. Input can be lists, lists of tuples, tuples, tuples of tuples, tuples of lists and arrays.

Python3

import numpy as np

ini_array = np.array(["1.1", "1.5", "2.7", "8.9"])

print ("initial array", str(ini_array))

# converting to array of floats
# using np.asarray
final_array = b = np.asarray(ini_array,
        dtype = np.float64, order ='C')

print ("final array", str(final_array))

Output

initial array ['1.1' '1.5' '2.7' '8.9']
final array [ 1.1  1.5  2.7  8.9]

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

Convert Python String Array to Array Float using np.asfarray

Here is the approach to convert an array of strings from Python to array float using np.asfarray(). The numpy.asfarray() function is used when we want to convert the input to a float-type array. Input includes scalar, lists, lists of tuples, tuples, tuples of tuples, tuples of lists, and arrays.

Python3

import numpy as np

ini_array = np.array(["1.1", "1.5", "2.7", "8.9"])

# printing initial array
print ("initial array", str(ini_array))

# converting to array of floats
# using np.asarray
final_array = b = np.asfarray(ini_array,dtype = float)

print ("final array", str(final_array))

Output

initial array ['1.1' '1.5' '2.7' '8.9']
final array [1.1 1.5 2.7 8.9]

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