>>> a = "545.2222"
>>> float(a)
545.22220000000004
>>> int(float(a))
545

I don't know what you mean: >>> a = '1721244344.700249000' >>> float(a) 1721244344.700249 These are all the decimal places. Trailing zeros will always be omitted as they are irrelevant. If you want to show them, do so when you output the value: >>> print(a.format("{:.9}")) 1721244344.700249000

For converting a string to float you can use float(). Eg.float('1.2123') You can not convert '*' into float because its an operator that's why error is coming.

#observe the code
volume = float(input("Enter volume of sphere in mm^3: "))

input() = Takes input from user and stores it in string

float() = It is used to convert strings to float

Your code is volume = float(input("Enter volume of sphere in mm^3: "))

1st input() takes input from user in string then float() converts it into float.

But a = 1.4*1.0e6 there is no input() function involved thats why it's a float.

You can simply achieve your work by

volume = eval(input("Enter volume of sphere in mm^3: "))

OR

volume = input("Enter volume of sphere in mm^3: ").split("*")
volume = float(volume[0])*float(volume[1])

split(separator)- It splits a string into an array of sub-strings, by a separator string provided by user

You can read about eval from here:- Read abut eval() from here

data-user_answers_id="5008">How To Convert a String to a Float in PythonIn this article, we'll explore how to convert strings to numbers using Python's float() function. Additionally, we'll learn how to convert numbers back to strings using Python's str() function.It's crucial to convert data types correctly before using them for calculations and combining them to avoid unexpected errors while the program is running.Using the float() function:In Python, you can change a string into a floating-point number using the float() function. This built-in function is designed to convert an object into a floating-point number. Essentially, the float() function invokes the specified object's float() function internally.ExampleLet's check out a simple example of converting a string to a float in Python:string_value = '9.56'float_value = float(string_value)print(type(float_value))print('Float Value =', float_value)OutputFloat Value = 9.56In this example, the float() function is used to convert the string "9.56" to a floating-point number. The resulting value is stored in the variable float_number.Why do we need to convert a string to float?When users provide float values through the terminal or when reading from a file, these values are initially in the form of string objects. To carry out operations like addition, multiplication, and more, it's important to convert these strings into float so that we can perform the required mathematical operations accurately.Examplevalue_1 = input('Please enter the first floating-point value:\n')value_1 = float(value_1)value_2 = input('Please enter the second floating-point value:\n')value_2 = float(value_2)print(f'Sum of {value_1} and {value_2} is {value_1 + value_2}')OutputPlease enter the first floating-point value:23.34Please enter the second floating-point value:365.34Sum of 23.34 and 365.34 is 388.6799The sum of 23.34 and 365.34 is calculated to be 388.6799.Using the str() function:We can also change a float to a string using the str() function. This becomes useful when we need to combine or concatenate float values with other strings.Example:value_1 = 1.23value_2 = 2.34value_3 = 3.45print(f'Concatenation of {value_1} and {value_2} is {str(value_1) + str(value_2)}')print(f'CSV from {value_1}, {value_2}, and {value_3}:\n{str(value_1)},{str(value_2)},{str(value_3)}')print(f'CSV from {value_1}, {value_2}, and {value_3}:\n{", ".join()}')OutputConcatenation of 1.23 and 2.34 is 1.232.34CSV from 1.23, 2.34, and 3.45:1.23,2.34,3.45CSV from 1.23, 2.34, and 3.45:1.23, 2.34, 3.45When we concatenate 1.23 and 2.34, the result is the string '1.232.34'. Additionally, this code generates two versions of comma-separated values (CSV).In the above program, if we skip converting floats to strings, the join() function will cause an exception. Additionally, using the + operator for concatenation won't work correctly, as it would attempt to add the floating-point numbers instead.Conclusion:In this tutorial, we've covered the conversion between strings and numbers in Python using the float() and str() functions. Ensuring proper data type conversion is crucial for accurate and error-free operations in a program.We started by exploring the float() function, which is used to convert strings to floating-point numbers. This is particularly important when handling user input or reading data from files where numeric values are initially in string form. We demonstrated its usage through examples, highlighting the significance of this conversion for mathematical operations.

if you really want to convert "1" of type str to 1 of type int then you can do something like that: ord("1")-48 this returns Unicode value of the digit, which is 48 for "0", 49 for "1", 50 for "2" etc. from that, it should be easy to create a floating point number in the for loop

You shouldn't call your variable sum, as that's a name of a built in function: https://docs.python.org/3/library/functions.html#sum Your problem however, stems from trying to add a string to a float. Could you please tell me, what is Adam + 5? Well, you can't, because it makes no mathematical sense. You didn't save the string representation str(sum), so sum never changed to a string What your research found is f-strings and they are very easy to use. Try: print(f"the sum of the values is {sum}") Simply, put an f before a string starts, then any string that you want goes between " and ", while any variables or other values go between { and }