Picture this: you’re extracting data from an XML file with a series of percentages. But your percentages look something like this:
You’ve successfully extracted the data, but these percentages are tagged with the “%” symbol, making them strings rather than numbers.
Now, let’s say you want to do something like:
percentage = "12%" if percentage < 15.0: print('Yay!')
But with that “%” symbol in the way, your Python code raises the
TypeError: '<' not supported between instances of 'str' and 'float'.
So, how can you transform these string percentages into numerical data and make your code run smoothly?
- String Replacement and Conversion to Float: Removes
'%'and converts the resulting string to float.
- Using String Slicing and Float Conversion: Slices off
'%'and converts the remaining string to float.
- Regular Expression-based Conversion: Uses a regular expression to remove
'%'and converts the result to float.
- Using List Comprehension for Bulk Conversion: A bulk conversion method that utilizes list comprehension to convert all percentages in a list to float.
Method 1: String Replacement and Conversion to Float
percentage = "-38%" percentage_num = float(percentage.replace('%', '')) print(percentage_num)
In this code,
replace('%', '') removes the ‘%’ symbol from the string, leaving just the numeric part. Then,
float() converts this string to a float number, which can be used for numerical comparisons.
If you want to convert to an integer, use the built-in
int() function instead.
Method 2: Using String Slicing and Float Conversion
You can utilize Python’s string slicing feature to omit the last character (the “%”) and then convert the remaining part to float.
percentage = "25%" percentage_num = float(percentage[:-1]) print(percentage_num)
percentage[:-1] is used to slice the string, excluding the last character (“%”). The result is then converted to a float using
🔗 Recommended: Introduction to Slicing in Python
Method 3: Regular Expression-based Conversion
This method uses the
re module, a powerful tool for handling strings. We’ll use a regular expression to remove non-numeric characters and then convert the result to float.
import re percentage = "4%" percentage_num = float(re.sub(r'[^0-9.-]', '', percentage)) print(percentage_num)
In this code,
re.sub(r'[^0-9.-]', '', percentage) replaces non-numeric characters with nothing, effectively removing them. We then convert the remaining string to a float.
Method 4: Using List Comprehension for Bulk Conversion
If we have a list of percentages, we can use list comprehension (combined with any of the above methods) to convert all percentages in one go.
percentages = ["-2%", "4%", "25%"] percentages_num = [float(p.replace('%', '')) for p in percentages] print(percentages_num)
[-2.0, 4.0, 25.0]
Here, we use list comprehension (
[float(p.replace('%', '')) for p in percentages]) to iterate over all percentages, remove the ‘%’ symbol, and convert the result to float.
💡 Recommended: List Comprehension in Python — A Helpful Illustrated Guide
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