Код:
a, b, c = map(float, input().split(' '))
Но при проверке на сайте следующая ошибка:
Traceback (most recent call last):
File "595bd828-ce3d-4d8b-9055-47517a8a18c0", line 3, in <module>
a, b, c = map(float, input().split(' '))
ValueError: could not convert string to float:
Я не могу понять, какие значения могут ее воспроизвести. По условию:
-10000<=a, b, c <=10000
Они могут быть любого типа (не только целые)
разделены пробелами
In this Python tutorial, we will discuss how to fix an error, “Could not convert string to float Python“.
In python, to convert string to float in python we can use float() method. It can only convert the valid numerical value to a floating point value otherwise it will throw an error.
Example:
my_string = '1,400'
convert = float(my_string)
print(convert)
After writing the above code (could not convert string to float python), Ones you will print ” convert ” then the output will appear as a “ ValueError: could not convert string to float: ‘1,400’ ”.
Here, we get the error because the value is not valid and we used a comma. You can refer to the below screenshot could not convert string to float python.
To solve this ValueError: could not convert string to float we need to give the valid numerical value to convert my string to float by using float() method.
Example:
my_string = '23.8'
convert = float(my_string)
print(convert)
After writing the above code (could not convert string to float python), Ones you will print ” convert ” then the output will appear as a “ 23.8 ”. Here, the float() method converts the string to float. You can refer to the below screenshot could not convert string to float python.
This is how to fix could not convert string to float python.
Read: Python find substring in string
How to fix could not convert string to float python
Let us see how to fix could not convert string to float python
In this example, we got a ValueError because the function argument is of an inappropriate type. So, when we tried to typecast a string value it throws ValueError.
Example:
str = "Hi"
print(float(str))
The normal text is not supported by the float() function in python. You can refer to the below screenshot for the error.
To fix value error: could not convert string to float python, we have to give numeric text value to convert it successfully to float. we can use the below code to solve the above error.
Example:
str = "5.45"
print(float(str))
You can refer to the below screenshot to see the output for how to fix could not convert string to float python.
You may like the following Python tutorials:
- How to handle indexerror: string index out of range in Python
- How to convert an integer to string in python
- Slicing string in Python + Examples
- Convert string to float in Python
Here we checked how to fix error, could not convert string to float python.
I am Bijay Kumar, a Microsoft MVP in SharePoint. Apart from SharePoint, I started working on Python, Machine learning, and artificial intelligence for the last 5 years. During this time I got expertise in various Python libraries also like Tkinter, Pandas, NumPy, Turtle, Django, Matplotlib, Tensorflow, Scipy, Scikit-Learn, etc… for various clients in the United States, Canada, the United Kingdom, Australia, New Zealand, etc. Check out my profile.
In Python, the ValueError: could not convert string to float
error occurs when you try to convert a string to a float, but the string cannot be converted to a valid float. In this tutorial, we will look at the common mistakes that could lead to this error and how to fix it with the help of examples.
Understanding the error
The float()
function in Python is used to convert a given value to a floating-point number. It takes a single argument which can be a number or a string. It is generally used to convert integers and strings (containing numerical values) to a floating-point number.
For a string to be successfully converted to a float in Python, it must contain a valid numerical value, which includes numerical values with a decimal point and/or a preceding sign (+ or -). If the string cannot be converted to a float value, it results in the ValueError: could not convert string to float
.
Common Scenarios for this error
The following are the common scenarios in which this error can occur when converting a string to float.
- The string contains non-numeric characters
- The string is empty
- The string contains multiple decimal points
- The string contains commas or other non-numeric characters
Let’s look at the above scenarios with the help of some examples.
# string contains non-numeric characters string_value = "abc123" float_value = float(string_value)
Output:
--------------------------------------------------------------------------- ValueError Traceback (most recent call last) Cell In[5], line 3 1 # string contains non-numeric characters 2 string_value = "abc123" ----> 3 float_value = float(string_value) ValueError: could not convert string to float: 'abc123'
Here, the string string_value
contains alphabetical characters and thus it cannot be converted to a floating-point number. You’ll also get this error for other non-numerical characters, for example, if your string has spaces (preceding, trailing, or, in the middle). The only non-numerical characters allowed are – a decimal point, a sign character (+ or -) present at the beginning, or an exponent character.
# the string is empty string_value = "" float_value = float(string_value)
Output:
--------------------------------------------------------------------------- ValueError Traceback (most recent call last) Cell In[6], line 3 1 # the string is empty 2 string_value = "" ----> 3 float_value = float(string_value) ValueError: could not convert string to float: ''
We get the same error with an empty string.
# string contains multiple decimal points string_value = "12.34.56" float_value = float(string_value)
Output:
--------------------------------------------------------------------------- ValueError Traceback (most recent call last) Cell In[7], line 3 1 # string contains multiple decimal points 2 string_value = "12.34.56" ----> 3 float_value = float(string_value) ValueError: could not convert string to float: '12.34.56'
The string in the above example contains multiple decimal points and is not a valid numerical value and thus we get the error.
# string contains other non-numerical characters like comma, etc. string_value = "1,000.0" float_value = float(string_value)
Output:
--------------------------------------------------------------------------- ValueError Traceback (most recent call last) Cell In[8], line 3 1 # string contains other non-numerical characters like comma, etc. 2 string_value = "1,000.0" ----> 3 float_value = float(string_value) ValueError: could not convert string to float: '1,000.0'
Although “1,000.0” can be considered as a valid numerical value but commas present in strings will cause this ValueError
when trying to convert it to a floating-point value.
Valid conversions
Let’s now also look at some cases where this error does not occur to understand what’s expected when converting a string to a float value.
# string is a valid integer string_value = "1234" float_value = float(string_value) print(float_value)
Output:
1234.0
In the above example, all the characters in the string are numerical characters; thus, we don’t get any errors converting it to a floating-point value.
# string is a valid real number string_value = "1234.75" float_value = float(string_value) print(float_value)
Output:
1234.75
We also don’t get an error for a string containing a valid real number with a decimal point.
# string contains a sign string_value = "+1234.75" float_value = float(string_value) print(float_value)
Output:
1234.75
Here, the string has a preceding sign and you can see that we don’t get an error. Note that if you use the sign incorrectly, you’ll get an error on converting it to a float value.
# string is in exponential notaion string_value = "1.23e-4" float_value = float(string_value) print(float_value)
Output:
0.000123
Exponential notation string value for a number is also valid when converting a string to a float.
How to Fix the Error?
To fix this error, make sure the string you are trying to convert contains a valid numerical value before converting it using the float()
function. There are many ways in which you can do so –
- Use a regular expression
- Use exception handling
Let’s look at both of these methods with the help of some examples.
Use a regular expression
Regular expressions (regex) are a sequence of characters that define a search pattern. They are used to match and manipulate text and are commonly used in programming languages and text editors.
You can use a regular expression to pattern match and extract valid numerical values from a string before applying the float()
function to convert them. This way you’ll only apply the float()
method to valid numerical strings and thus can avoid the ValueError: could not convert string to float
error.
To extract only numbers (optionally with a decimal point and a preceding + or – sign), you can use the following regular expression:
[-+]?[0-9]*.?[0-9]+
This regular expression matches:
[-+]?
: an optional + or – sign[0-9]*
: zero or more digits.?
: an optional decimal point[0-9]+
: one or more digits
This regular expression will match numbers such as 123
, -45.67
, +89.0
, and 0.123
.
Let’s look at an example.
import re # pattern to look for valid_num_pattern = r'[-+]?[0-9]*.?[0-9]+' # the string value string_value = "abc 123.45+234.12" # extract the numbers nums = re.findall(valid_num_pattern, string_value) # show the extracted numbers print(nums)
Output:
['123.45', '+234.12']
In the above example, we are using the findall()
function from the re
module to find all the matches for a valid number in a string, it returns a list of all the valid string numbers. You can now go ahead and apply the float()
function on each of the values in the returned list to convert them to floating-point values.
result = [float(val) for val in nums] print(result)
Output:
[123.45, 234.12]
You can see that we don’t get an error here.
Use exception handling
Alternatively, you can use error handling to detect this error and then perform corrective steps, for example, not converting the string to a float or maybe extracting the numeric values only from the string, etc.
Let’s look at an example.
string_value = "abc1234" try: float_value = float(string_value) except ValueError: print("Cannot convert string to float")
Output:
Cannot convert string to float
Here, we are catching the error and displaying a message that the string value could not be converted to a float value.
Conclusion
The ValueError: could not convert string to float
error occurs when you try to convert a string to a float, but the string cannot be converted to a valid float. To fix this error, you need to check the string for non-numeric characters, empty values, multiple decimal points, and commas or other non-numeric characters. You can use a regular expression to extract only valid numerical values from the string. You can also use error handling to avoid this error. By following the steps outlined in this tutorial, you can easily fix this error and continue working with numerical data in Python.
You might also be interested in –
- How to Fix – TypeError: can only concatenate str (not ‘int’) to str
- How to Fix – TypeError ‘float’ object is not subscriptable
- How to Fix – TypeError ‘set’ object is not subscriptable
-
Piyush is a data professional passionate about using data to understand things better and make informed decisions. He has experience working as a Data Scientist in the consulting domain and holds an engineering degree from IIT Roorkee. His hobbies include watching cricket, reading, and working on side projects.
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Table of Contents
Hide
- ValueError: could not convert string to float
- Exception could not convert string to float
- Fix ValueError: could not convert string to float
- Solution 1: Ensure the string has a valid floating value
- Solution 2: Use try-except
If you convert a string object into a floating-point in Python many times you will get a ValueError: could not convert string to float. Usually, this happens if the string object has an invalid floating value with spaces or comma Python will throw ValueError while parsing into string object into float.
In this article, we will take a look at what this error means and how to fix this error in your code with examples.
If we are reading and processing the data from excel or CSV, we get the numbers in the form of a string, and in the code, we need to convert from string to float.
Python has a built-in float()
method that can parse the string to a floating-point number. This method will be useful when we need to perform a mathematical operation on a string object.
The float()
method only allows you to convert strings that hold float-like numbers. This means that you cannot convert a value if
- A value contains spaces
- A value contains a comma
- A value contains special characters
Exception could not convert string to float
order_value = '12,000'
tax_percentage = 4
tax_amount = (float(order_value)*(tax_percentage / 100))
print("The total tax amount is ", tax_amount)
Output
Traceback (most recent call last):
File "c:/Projects/Tryouts/main.py", line 4, in <module>
tax_amount = (float(order_value)*(tax_percentage / 100))
ValueError: could not convert string to float: '12,000'
Let’s take a simple example to demonstrate the ValueError exception. In the below code, we have the total order value in terms of USD, and we are accepting this in string format and performing a tax calculation.
If you see the above code, the order value has a comma-separated numeric value, and while parsing into a float, Python will throw ValueError: could not convert string to float.
There are a few other scenarios where you could get ValueError.
- Converting an empty string into a floating-point number
- Converting a non-floating string to a floating-point number
Fix ValueError: could not convert string to float
There are multiple ways to resolve the issue. Let’s take a look at each of the solutions.
Solution 1: Ensure the string has a valid floating value
The easiest way is to clean up the data or pass it in the correct format if we already know the data format before converting it into float.
If the value has a comma, space, or any special characters, then it needs to be processed before converting into float.
In the below code, we are storing a valid float number as a string, and later we are converting that into floating-point to calculate tax.
Example:
order_value = '12000'
tax_percentage = 4
tax_amount = (float(order_value)*(tax_percentage / 100))
print("The total tax amount is ", tax_amount)
Output
The total tax amount is 480.0
Solution 2: Use try-except
The best way is to handle the exception in case of an invalid data format. In the below code, it will run the code in the try block. If the conversion fails, then it runs the except block code.
Example:
order_value = '12,000'
tax_percentage = 4
try:
tax_amount = (float(order_value)*(tax_percentage / 100))
print("The total tax amount is ", tax_amount)
except:
print ("Order value is invalid")
Output
Order value is invalid
Srinivas Ramakrishna is a Solution Architect and has 14+ Years of Experience in the Software Industry. He has published many articles on Medium, Hackernoon, dev.to and solved many problems in StackOverflow. He has core expertise in various technologies such as Microsoft .NET Core, Python, Node.JS, JavaScript, Cloud (Azure), RDBMS (MSSQL), React, Powershell, etc.
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In Python, the string is the sequence of alphabets or numbers enclosed in quotation marks, and the float value is any positive or negative number containing a decimal point. To perform various mathematical operations, fractional strings must be converted to float data types. However, while converting string values to float, users might encounter the “ValueError” due to irrelevant symbols and characters. To fix this error, various functions are used in Python.
This write-up will present the causes and solutions for the “ValueError: could not convert string to float” with appropriate examples. The following terms are discussed in this Python blog post in detail:
- Reason: Incorrect String Initializing
- Solution 1: Using re.findall() Function
- Solution 2: Using str.replace() Function
- Solution 3: Using try/except Block
So let’s get started!
Reason: Incorrect String Initializing
The “ValueError: could not convert string to float” occurs in Python due to the incorrect initialization of value to a string variable. The string to be converted must not contain any characters or symbols. Only numeric values will be passed inside the string to convert into float. The incorrect string initialization is shown in the below snippet:
The above output shows the string value containing symbols, characters, and numeric values.
Solution 1: Using re.findall() Function
The “re.findall()” function is used in Python to find all the matched patterns and return all non-overlapping matches of the pattern in a list of strings. Let’s have a look at the below code to extract the float value:
Code:
import re Value2 = 'xyz2.23' Output = re.findall(r'd+.d+', Value2) print(Output) float_value = float(Output[0]) print(float_value)
In the above snippet:
- The “re.findall()” function is used to find all the digits in the given string using the pattern “d+.d+”.
- The “re.findall()” function returns a list of strings, and the returned list is converted into float value using the inbuilt “float()” function.
Output:
The above output shows the list of strings followed by the float value.
Solution 2: Using str.replace() Function
The “str.replace()” function is also used to fix the “ValueError: could not convert string to float” by replacing any symbols or characters with an empty string. In the below snippet, the “str.repalce()” function is used to replace the unwanted symbols and strings:
Code:
Value = '9.94%' float_value = float(Value.replace('%', '')) print(float_value) print(type(float_value))
In the above snippet:
- The “str.replace()” function takes two parameter values. The first parameter takes the substring value or old value that needs to be replaced. A second parameter specifies the new value that will replace the old one.
- The second parameter is an empty string which means that all the unwanted symbols and characters will be replaced with an empty string.
- The inbuilt “float()” function converts the newly created strings into floats.
Output:
In the above output, the string value has been converted into float successfully.
Note: The “str.strip()” function removes the leading and trailing characters or symbols from the given string. This method can not remove the characters placed in between the string.
Solution 3: Using try/except Block
The “ValueError” can also be removed using the “try/except” block in Python. An example of this is shown in the below snippet:
Code:
Value = '%9.9%4%' try: Output = float(Value) except ValueError: Output = float(Value.replace('%', '')) print(Output) print(type(Output))
In the above code snippet:
- The string value containing symbols and digits is initialized.
- The try-except block handles the “ValueError” along with the combination of the “str.repalce()” function.
- After replacing the unwanted symbols in the except block, the “float()” function converts the string into float.
Output:
The above output verified that the string value had been converted into a float value.
That’s it from this guide!
Conclusion
To fix the “ValueError: could not convert string to float”, the “str.repalce()”, “re.findall()” and “try-except” is used in Python. The “re. findall()” and “str.repalce()” functions are used to remove symbols and characters from the given string. The “float()” function is used along with the combination of both these functions to convert the string value into float. The try-except block is also beneficial to rectify or handle this error in Python script. This Python write-up presented a complete guide on how to fix the “could not convert string to float” error.