Why my list is not being converted to a float

Question

I have the list of [0.5, 1.5, 2.5, 3.5].

def calc_mean(arglist):
    return sum(arglist)/len(arglist)

print(calc_mean([0.5, 1.5, 2.5, 3.5]))

I have another list, strlist = ['0.5','1.5','2.5','3.5'] and I need to convert the elements in it to floats and then calculate the average but I’m getting the error:

unsupported operand type(s) for +: 'int' and 'str') because the line return sum(arglist)/len(arglist) is working with integers and strlist is a string why strlist isn’t being converted to a float and it’s being treated as a str even though I converted it using [float(i) if ‘.’ in i else int(i) for i in strlist]

def str2float(strlist):
   flist = [float(i) if '.' in i else int(i) for i in strlist] 
   return flist

strlist =  ['0.5','1.5','2.5','3.5']
print(str2float(strlist))
print(calc_mean(strlist))

Asked By: HAZEM

||

Source

Answer 1

print(calc_mean(strlist))

As noted in comments, you have not converted strlist before passing it to calc_mean.

print(calc_mean(str2float(strlist)))

Answered By: Chris

Answer 2

According to @craigb and @Chris, you have to call the conversion function first and then the averaging function.

print(calc_mean(str2float(strlist)))

If you want to rewrite the code so that you simply automate this control, you can do it in several ways, for example:

def calc_mean(arglist):
    try:
        return sum(arglist) / len(arglist)
    except TypeError:
        recasted_list = str2float(arglist)
        return sum(recasted_list) / len(recasted_list)

Also, I suggest rewriting the recast function in a simpler and robust way like this:

def str2float(strlist):
    return [float(i) for i in strlist]

It can be done in many other ways of course, but it always depends on the extent of the upstream problem you want to solve.

Answered By: Giuseppe La Gualano

Why my list is not being converted to a float

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