str() Error?

Question

Why I cannot change a list into a string by str() in Python3
Also, how to do it

Answer 1

A =[1,2,3]
S = str(A)

print(S)

The output is already string. But it is formated like list.

If you want to put only values from list to string then:
S = ''.join(str(e) for e in list)

Note that '' is two ' '

Answer 2

a =[1,2,3]
b = str(a)

print(b)

if you need it as separated values you can remove the brackets with .replace("[", "")
or if you want all the values to be one long string you can do
a = [1,2,3]
s = ""
for i in a:
i = str(i)
s += i