Convert String to Float (with calculation within the string)

Question

I want a String to be converted to a float and if the string contains a calculation (like 1/3) it should calculate it and then convert.

I've tried by entering float(y), whereas y is my '+1/3'.

y = '+1/3'
float(y)

I expected the output to be something like '0.3333', but the error message i keep getting is "ValueError: could not convert string to float: '+1/3'".

can you guarantee that you will always have `/` in your string? — lmiguelvargasf, Sep 10 '19 at 20:18
The `float` initializer doesn't evaluate expressions if the arugment passed to it is a string. What version of Python are you using? — martineau, Sep 10 '19 at 20:42

score 0 · Answer 1 · answered Sep 10 '19 at 20:20

0

have you tried with eval?

eval("+1/3")

output

0.3333333333333333

answered Sep 10 '19 at 20:20

NicoT

using eval is not a good practice, you read more about that [here](https://stackoverflow.com/questions/1832940/why-is-using-eval-a-bad-practice). – lmiguelvargasf Sep 10 '19 at 20:22

score 0 · Answer 2 · answered Sep 10 '19 at 20:21

0

Let's assume you are going to have / in your string, so you can use the following code:

numerator, denominator = '+1/3'.split('/')
y = float(numerator) / float(denominator)

answered Sep 10 '19 at 20:21

lmiguelvargasf

what if operator changes? like * + - – vb_rises Sep 10 '19 at 20:21
@vbrises, can you provide a concrete input? – lmiguelvargasf Sep 10 '19 at 20:22

2 Answers2