How Can I Efficiently Extract Floating-Point Numbers from Strings in Python?

How to Extract Floating-Point Numbers from Strings with Precision

In certain scenarios, extracting floating-point numbers from strings is necessary. For instance, you may encounter strings like "Current Level: 13.4 db." where only the numerical value is of interest. Regular expressions (RegEx) offer a straightforward solution for this task.

RegEx Approach

If your floating-point numbers always appear in the form "a.b," you can utilize the following RegEx pattern:

re.findall("\d+\.\d+", "Current Level: 13.4db.")

This pattern will capture any numerical sequence containing one or more digits, followed by a decimal point, and then one or more digits. In our example, it will return the string '13.4'.

Advanced RegEx for Robust Extraction

For greater flexibility, consider the following pattern:

re.findall(r"[-+]?(?:\d*\.*\d+)", "Current Level: -13.2db or 14.2 or 3")

This pattern handles a wider range of floating-point representations, including:

• Negative signs (-)
• Whole numbers (e.g., "3")
• Numbers without decimal points (e.g., "13")

It will return a list of all matched numbers: ['-13.2', '14.2', '3'].

Direct Conversion for Validation

Alternatively, you can directly convert a token to a float to validate user input:

user_input = "Current Level: 1e100 db"
for token in user_input.split():
    try:
        print(float(token), "is a float")
    except ValueError:
        print(token, "is something else")

This code attempts to convert each token in the input string to a float and prints whether the token is a valid float or not.

By leveraging the appropriate method for your specific requirements, you can effectively extract floating-point numbers from strings with the desired precision and flexibility.

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