Python | Convert Joint Float string to Numbers

Sometimes, while working with Legacy languages, we can have certain problems. One such can be working with FORTRAN which can give text output (without spaces, which are required) '12.4567.23' . In this, there are actually two floating point separate numbers but concatenated. We can have problem in which we need to separate them. Lets discuss certain ways in which this task can be performed.

Method #1 : Using loop + float() 
This is brute force method in which this task can be performed. In this, we iterate for each element and break in chunks of 4 and skip to every 5th element and perform split and store in list. The conversation from string to float is done using float().
 

# Python3 code to demonstrate working of 
# Convert Joint Float string to Numbers
# Using loop + float()

# initializing string
test_str = "45.6778.4524.45"

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

# Convert Joint Float string to Numbers
# Using loop + float()
res = []
for idx in range(0, len(test_str), 5):
    res.append(float(test_str[idx : idx + 5]))

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

The original string is : 45.6778.4524.45
The float list is : [45.67, 78.45, 24.45]

 
Method #2 : Using list comprehension + float() 
This is shorthand way to solve this problem. This is similar to above function. The difference is that we perform all loop task in single line using list comprehension.
 

# Python3 code to demonstrate working of 
# Convert Joint Float string to Numbers
# Using list comprehension + float()

# initializing string
test_str = "45.6778.4524.45"

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

# Convert Joint Float string to Numbers
# Using list comprehension + float()
res = [float(test_str[idx : idx + 5]) for idx in range(0, len(test_str), 5)]

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

The original string is : 45.6778.4524.45
The float list is : [45.67, 78.45, 24.45]

Here's another approach using the re module in python:

# Approach 3: Using regex
import re

test_str = "45.6778.4524.45"

# Split the string using a regex pattern that matches 5 characters that starts with a digit
# and ends with a dot
res = [float(x) for x in re.findall(r'\d+\.\d{2}', test_str)]

print("The original string is :", test_str)
print("The float list is :", res)

The original string is : 45.6778.4524.45
The float list is : [45.67, 78.45, 24.45]

This approach uses the re module to split the string using a regex pattern. The pattern matches 5 characters that start with a digit and end with a dot, which corresponds to a float number with two decimal places. The re.findall function returns a list of all the matches, which are then converted to float numbers.

Time Complexity: O(n), where n is the length of the input string test_str.
Auxiliary Space: O(m), where m is the number of matches found in test_str.

Approach 4: Using the re module and a loop

Step-by-step approach:

1. Define the input string.
2. Create an empty list to store the float values.
3. Use a regular expression to find the first float value in the input string.
4. Convert the found float value to a float and append it to the list of float values.
5. Remove the found float value from the input string.
6. Repeat steps 3-5 until no more float values can be found in the input string.
7. Print the original string and the list of float values.

Below is the implementation of the above approach:

import re

test_str = "45.6778.4524.45"
float_list = []

while True:
    match = re.search(r'\d+\.\d{2}', test_str)
    if match is None:
        break
    float_value = float(match.group())
    float_list.append(float_value)
    test_str = test_str[match.end():]

print("The original string is:", test_str)
print("The float list is:", float_list)

The original string is: 
The float list is: [45.67, 78.45, 24.45]

Time complexity: O(n^2), where n is the length of the input string.
Auxiliary space: O(n), to store the list of float values.

Method 5 :  Use the numpy module

Step-by-step approach:

Import the numpy module.
Initialize the input string test_str.
Print the original input string.
Use the numpy.fromstring() function to convert the input string to a numpy array of floats.
Print the resulting numpy array converted to a list of floats

# importing numpy module
import numpy as np

# initializing string
test_str = "45.6778.4524.45"

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

# Convert Joint Float string to Numbers
# Using string slicing and numpy.fromiter()
chunk_size = 5
chunks = (test_str[i:i+chunk_size] for i in range(0, len(test_str), chunk_size))
res = np.fromiter(chunks, dtype=np.float32)

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

OUTPUT:
The original string is : 45.6778.4524.45
The float list is : [45.67, 78.45, 24.45]

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

Auxiliary space: O(n), where n is the length of the input string, as the numpy array created from the input string has the same length as the input string.