Python: String will not convert to float [duplicate]

Answer 1

float(line) doesn't change line at all, so it is still a string. You'll want to use line = float(line) instead.

Answer 2

float() returns a float, not converts it. Try:

line = float(line)

Answer 3

float(line) does not convert in-place. It returns the float value. You need to assign it back to a float variable.

float_line = float(line)

UPDATE: Actually a better way is to first check if the input is a digit or not. In case it is not a digit float(line) would crash. So this is better -

float_line = None
if line.isdigit():
    float_line = float(line)
else:
    print 'ERROR: Input needs to be a DIGIT or FLOAT.'

Note that you can also do this by catching ValueError exception by first forcefully converting line and in except handle it.

try:
    float_line = float(line)
except ValueError:
    float_line = None

Any of the above 2 methods would lead to a more robust program.