ValueError could not convert string to float occurs when we tried to convert a string into float. In Python, a string can be converted into a float value only if the string has numeric values. If the string contains characters and we try to convert the string into floating, we will get ValueError: could not convert string to float error.
If the following mentioned methods couldn’t help you to solve the problem, please let us know through comments and we will try our best to help you.
ValueError Could Not Convert String to Float
The ValueError: could not convert string to float error occurs when we convert the string data type into the floating when the string has some characters. In Python, the strings can be easily converted into the float data type if the string has only numeric values. Moreover, there can be a number of reasons for getting ValueError: could not convert string to float error. Some of these are listed below:
- Empty string conversion
If you try to convert a string into a floating point that does not have anything, then you will get this error. Let us take an example.
# empty string
string =""
# converting the string into float
f = float(string)Output:
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
/tmp/ipykernel_156831/3839707386.py in <module>
3
4 # converting the string into float
----> 5 f = float(string)
ValueError: could not convert string to float: ''As you can see, we get the error because an empty string cannot be converted to a numeric value.
- Converting special characters along with numeric values
Sometimes, we forget about the special characters. Special characters cannot be converted directly into numeric values. So, if the string has numeric values along with special characters, we will get ValueError: could not convert string to float error. See the example below:
# empty string
string ="12.4%"
# converting the string into float
f = float(string)Output:
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
/tmp/ipykernel_156831/599800528.py in <module>
3
4 # converting the string into float
----> 5 f = float(string)
ValueError: could not convert string to float: '12.4%'See that because of the special character, we are getting this error.
- Converting a character to float
Characters other than numeric values cannot be converted into floating points. For example, the following string has a character that cannot be converted into floating points:
# empty string
string ="Bashir"
# converting the string into float
f = float(string)Output:
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
/tmp/ipykernel_156831/1357347263.py in <module>
3
4 # converting the string into float
----> 5 f = float(string)
ValueError: could not convert string to float: 'Bashir'
Now, let us go through some of the solutions to solve the error:
Removing all the special characters from the string
As we know the error is because of the characters that cannot be converted into float. So, in order to convert the string into a floating point, we have to remove those characters. If you have a string value that contains numbers with some special characters, then it is highly recommended to remove the special characters from the string before converting it to float.
In this section, we will learn how we can use regular expressions to remove special characters from the string and convert only the numeric values into floating data types.
# importing the module
import re
# string
input_string ='x32.32%'
# removing all the special characters
to_convert = re.findall(r'\d+\.\d+', input_string)
# convertint string into float
converted =float(to_convert[0])
# printing
print(converted)Output:
32.32Notice that we were able to convert the string into a floating data type without getting ValueError: could not convert string to float error.
Using strip() function
Another method to get rid of ValueError: could not convert string to float error is to use the strip() function to remove any special characters from the string and convert the remaining part of the string into floating.
For example, see the following code:
# string
input_string ='32.32%'
# converting string into numeric values
converted =float(input_string.strip('.%'))
# printing
print(converted)Output:
32.32Notice that we have successfully removed the special character from the string before converting it into the floating point.
Using replace() method
Another way is to use the replace() method to replace unnecessary characters and replace them with an empty string. For example, consider the following Python code:
# string
input_string ='32.32%'
# replacing special character
to_convert = input_string.replace('%', '')
# coverting string to float
converted = float(to_convert)
# printing
print(converted)
Output:
32.32Notice that we first replaced the special character with an empty string and then converted the string into a floating point. That is why we didn’t get the ValueError: could not convert string to float error.
Using try-except to handle error
If you are taking input from the user and are not sure what kind of characters will be there, then you can use the try-except block in order to handle if an error occurs.
The code will first, enter the try block and if an error occurs, then rather than crashing the script, the except block will be executed as shown below:
# empty string
string ="Bashir"
# using try block
try:
# converting the string into float
f = float(string)
# except block
except:
print("Cannot covert the given string into float")
Output:
Cannot covert the given string into floatAs you can see, we handled the error successfully.
Understanding the error
Now let us try to understand what the error means. In Python, usually, the errors have two main parts. The first part of the error shows the category of the error which in this case is the ValueError which means there is an error because of misuse of values. The second part of the error gives more specific information and tells us what type of value error is there. In this case, it says that cannot convert the string to float which means somewhere in our code, we are trying to convert the string into floating and it was unsuccessful. There can be various reasons for ValueError: could not convert string to float error some of which are:
- The string can be empty
- The string has special characters that cannot be converted into floating points
- The string might have non-numeric characters
How to solve ValueError In Python?
The ValueError, as the name suggests raises when a wrong value is assigned to an object in Python. For example, we cannot directly convert a string into a floating value because of ValueError.
The simplest way to solve the ValueError is to assign the correct value to the correct object. You can find the type of the object using the type() method.
What is a float in Python?
Float is a data type in Python. It simply represents the decimal values. Any numeric value with decimal points in Python is considered to be a floating data type.
The following are some examples of float data types in Python:
# floating points
x = 9.3
y = 4343.0
z = 0.09What is a string in Python?
A string is also a data type in Python. Any value that is inside quotation marks in Python is considered to be a string. The quotation marks can be either double or single.
The following are some of the examples of strings in Python:
# examples of strings in python
x = "bashir"
y = "33435"
z= "23.423"
t = "[2,4,5,6]"
Summary
In this short article, we discussed how we can solve ValueError: could not convert string to float error using various methods. We covered four different methods to solve the ValueError: could not convert string to float error by taking examples. Moreover, we also discussed how to understand errors in Python so that we can easily solve them.