Converting a string separated by commas to a list of floats

x is a list with one string, so to access that string you need x[0]. That string is comma-separated, so you need to specify the delimiter: split(','). (Otherwise, split() tries to split a string on whitespace, as described in the docs.)

So you end up with:

[float(i) for i in x[0].split(',')]

You can use map() like this:

list(map(float, x[0].split(',')))

map() takes a function (float in our case) and an iterable ( in our case this list: x[0].split(',')). float function is called for each item of our list x[0].split(',')

It is equivalent to this list comprehension:

[float(item) for item in x[0].split(',')]

Split the string by commas, and construct a float from each item:

[ float(item) for item in '1.1,2.3,5.1'.split(',') ]

Make sure you are applying your split() function on a string and not the single element list. Use x[0] to ensure that. Also, pass a separator , to the split() function.

x = [float(i) for i in x[0].split(',')]

x=[float(i) for i in x.split()] is almost correct, except for two things. For one, you're not passing in anything to the split() function, so it's not going to split anything in your string (it would split only on whitespace, which your string does not have). You want to split by commas, so you have to pass a comma to it, like x.split(',').

Second, seeing as x is defined by x= ['1.1,1.2,1.6,1.7'], which is a list containing a single string, you would have to refer to the string in the array with x[0]. The final code would look like this:

x = ['1.1,1.2,1.6,1.7']
floats = [float(i) for i in x[0].split(',')]
print(floats)

This outputs a list of floats: [1.1, 1.2, 1.6, 1.7]

If x were just a string, like x = '1.1,1.2,1.6,1.7', then you would simply use floats = [float(i) for i in x.split(',')].