Python valueerror: could not convert string to float Solution

Python supports type conversion in which Python provides us different inbuilt methods such as float(), str(), bool(), int(), etc. to convert a data type of an object. There are some rules associated with Python data type conversion, and if we make some mistake with them, we get the valueerror.

In this Python tutorial, we will discuss the Python “valueerror: could not convert string to float” error, which occurs when we try to convert an invalid string number to a floating-point number using the float() function. Also, we will walk through some examples which demonstrate this error in Python and show how to solve it.

The Python Error: valueerror: could not convert string to float

The error statement valueerror: could not convert string to float is divided into two statements.

1. ValueError : It is a type of error in Python that occurs when we mishandle the values and datatype in Python .
2. could not convert string to float : It is the error message that tells us that Python is unable to convert a given string to a float number because of some value conversion error.

Reason

Python provides a float() function that can convert a valid number into a floating-point number, and the number could be a valid string number or an integer number.

Example

>>> int_num = 3045   #integer number
>>> float(int_num)   # convert the integer number to float number
3045.0

>>> str_num = '30846.34'   #string number
>>> float(str_num)     # convert the string number to float number
30846.34

The float() function is only able to convert a string number into a float number if the string number is a valid number and "inf"(for infinity). If the string contains any of the following characters:

• Any space character.
• Any commas or letters.
• Or any special character (except _ underscore).

Then it will throw the valueerror: could not convert string to float error.

Example 1

>>> str_num = '23 34' #contain space
>>> float(str_num)

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: could not convert string to float: '23 34'

Example 2

>>> str_num = '23M' #contain letters
>>> float(str_num)

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: could not convert string to float: '23M'

Example 3

>>> str_num = '23,&' #contain special characters
>>> float(str_num)

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: could not convert string to float: '23,&'

Most Common Scenario

The most common case where many new programmers face this error is when they input the number from the user and convert it into float using the float() function wrapped around the input() function. If the user inputs an invalid number, the float() conversion fails, and we receive an error.

For example

Dollar = float(input("Enter the dollar eg(34334): "))

INR = Dollar * 74.43

print(f"${Dollar} = {round(INR,2)}R")

The above program converts the user's entered dollars into the Indian rupee. If the user inputs an invalid dollar amount, such as 345,223 it will throw the error because Python float cannot convert comma-separated string numbers into float.

Output

Enter the doller eg(34334): 345,223
Traceback (most recent call last):
File "main.py", line 1, in <module>
Dollar = float(input("Enter the dollar eg(34334): "))
ValueError: could not convert string to float: '345,223'

Solution

The above program will work fine if the user enters the value of Dollar correctly, but when we create a program , we can not blame the user for such a logical error. We have to keep in mind the possibility that the user will enter the wrong amount. In that case, we can use Python error handling using Python to try and except keywords. And to make the amount enter readability, we can ask the user to use an underscore _ instead of a comma , to separate the amount.

Example

try:
    Dollar  = float(input("Enter the dollar eg(334_334): $"))
    INR = Dollar * 74.43
    print(f"${Dollar} = {round(INR,2)}R")

#if there is an error in the program
except:
    print("Enter a valid amount as specified")

Output

Enter the dollar eg(334_334): $343_343
$343343.0 = 25555019.49R

Conclusion

In this Python error debugging tutorial, we learned about valueerror: could not convert string to float and its solution. This error occurs when we try to type convert a string value to a float number using the float() function, and the string number is not a valid number. This error is pretty common and you often encounter it when you are a beginner learner of Python.

To debug this error, you just need to make sure that the string you are converting is a valid number, and you can always use the try-except method.

If you are still getting this error in your program, please comment down your query and source code in the comment section. We will try to help you in debugging.

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