Check if a string can be converted into float in Python

In this Python tutorial, we will discuss, how to check if a string can be converted into a float.

Table Of Contents

Using Regex to check if string can be converted into a float

In Python, using the regex module’s match() function, we can check if a string matches the given regex pattern or not. We will use a regex pattern to check if string is a float or not. If the match() returns a Match object then it means string can be converted into a float.

Regex Pattern to match float

'[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?$'

Let’s see the complete example,

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import re

def isFloat(strValue):
    # Check if a string can be converted into a float
    if (re.match(r'[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?$', strValue) is not None):
        print('Yes, \"', strValue, '\" can be converted into float')
    else:
        print('No, \"', strValue, '\" can not be converted into float')

isFloat('10')
isFloat('10.67')
isFloat('10.67 Dollars')
isFloat('-10.67')
isFloat('10.6e6')
isFloat('Total 10.67')

Output:

Yes, " 10 " can be converted into float
Yes, " 10.67 " can be converted into float
No, " 10.67 Dollars " can not be converted into float
Yes, " -10.67 " can be converted into float
Yes, " 10.6e6 " can be converted into float
No, " Total 10.67 " can not be converted into float

It covered all the formats of floats. So, this is the best method to check if a string can be converted into a float or not.

Using replace() and isdigit() to check if string can be converted into a float

To check if a string can be converted into a float, remove the first dot (.) from the copy of string and then check if all the remaining characters are digit only. If yes, then it means string can be converted into a float.

To remove the first occurrence of ‘.’ from string, replace that with an empty string using replace() function. Then check if all the remaining characters are digit only using the isdigit() function.

Let’s see an example, where we will check if string ‘100.456’ can be converted into a float or not.

Example 1:

strValue='100.456'

# Check if a string can be converted into a float
if strValue.replace('.', '', 1).isdigit():
    print('Yes, this string can be converted into float')
else:
    print('This string can not be converted into float')

Output:

Yes, this string can be converted into float

It shows that the string ‘100.456’ can be converted into a float. Now let’s see a negative example,

Example:2

Let’s see an example, where we will check if string ‘100 Dollars’ can be converted into a float or not.

strValue='100 Dollars'

# Check if a string can be converted into a float
if strValue.replace('.', '', 1).isdigit():
    print('Yes, this string can be converted into float')
else:
    print('This string can not be converted into float')

Output:

This string can not be converted into float

It shows that the string ‘100 Dollars’ can not be converted into a float.

Using float() to check if string can be converted into a float

Try to convert the string into a float using the float() function. If string can be converted into a float, then it will return a float number, otherwise it will raise an exception. So, we can use the try/except block to check if a string contains a float or not.

Let’s see an example, where we will check if string ‘12.56’ can be converted into a float or not.

strValue='12.56'

# Check if a string can be converted into a float
try:
    float(strValue)
    print('Yes, this string can be converted into float')
except:
    print('This string can not be converted into float')

Output:

Yes, this string can be converted into float

It shows that the string ‘12.56’ can be converted into a float.

Summary

In this article, we learned about three techniques to check if a string can be converted to float or not. Thanks

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