Use numbers in a string input, Python 3

Question

I want to export and use numbers in a string in Python 3.

for example

_input = input()
>? circle(5)

I want to export and use 5 as float here.

I tried to use _input.split('circle(') but it makes a list with 2 elements ['', '5)'] I tried to use _input.split(')') an, it makes another list with 2 elemtens ['circle(5', '']

Is there any module that helps me to do it or I should use split in another way ?

After this, what if I want to use 2 numbers ?

for example

_input = input()
>? circle(5,3.14)

or

_input = input()
>? circle(5, 3.14)

and then multiply this numbers ( 5 * 3.14 )

Maybe it's because I'm tired. But I don't follow at all what you're trying to do. — vallentin, Apr 11 '17 at 08:51
@Vallentin Im trying to make a shape calculator, I want user enter the shape name and numbers like this — DarkSuniuM, Apr 11 '17 at 08:55
If you want to create some sort of calculator, you'll either need a syntax parser (not so easy) or somehow implement this with `eval` (might be simpler but less clean) — Elmar Peise, Apr 11 '17 at 09:00

spadarian · Answer 1 · 2017-04-11T09:06:37.583

1

Probably regular expressions is the best alternative

import re
input_ = 'circle(5, 3.14)'
numbers = re.findall('\\d+[.]*\\d*', input_)
float(numbers[0]) * float(numbers[1])

edited Apr 11 '17 at 09:06

answered Apr 11 '17 at 08:58

spadarian

1,604
10
14

I would parse the statement, but not search for integers – Piotr Pęczek Apr 11 '17 at 09:00
It works, can u explain me that ('\\d+[.]*\\d*', input_) ?? – DarkSuniuM Apr 11 '17 at 12:07
1

The regular expression should be read like: Any digit (\\d), appearing 1 or more times (+), followed by a stop ([.]) appearing 0 or more times (*), followed by any digit (\\d) appearing 0 or more times (*) – spadarian Apr 12 '17 at 01:28

score 1 · Accepted Answer · edited May 23 '17 at 12:10

1

If there will be just one function with brackets then use this. First we extract string inside the bracket. Now it'll be easy for us to do whatever we want with the string.

s=input()
string_in_brack = s[s.find("(")+1:s.find(")")]
numbers = string_in_brack.split(',')
if len(numbers)>1:
    float(numbers[0]*numbers[1])
else:
    float(numbers[0])

String in brack function taken from here. What you do is you first search for the opening bracket '(' and then you slice the string till where the closing bracket is found ie ')'. Suppose string is s='blahblah' then s[4:7] will return 'bla' etc..

edited May 23 '17 at 12:10

Community

1
1

answered Apr 11 '17 at 09:06

Abhishek J

2,386
2
21
22

Thanks alot, It works good, Can u give me a resource about this part ? => `[s.find("(")+1:s.find(")")]` – DarkSuniuM Apr 11 '17 at 12:19
1

@AlirezaAyinMehr Your welcome and check the edit and the link I attached.. – Abhishek J Apr 12 '17 at 04:17

score 1 · Answer 3 · answered Apr 11 '17 at 09:07

Hardcode-y way to parse your string:

>>> s = 'circle(5, 3.14)'
>>> a, b = map(float, s.strip()[7:-1].split(','))
>>> a
5.0
>>> b
3.14
>>> a*b
15.700000000000001

i.e. take the number part, split by comma, turn the list elements to floats and multiply them.

Using a regex might be more easily translatable to similar problems:

>>> import re
>>> s = 'circle(5, 3.14)'
>>> a, b = re.match('\s*circle\((\d(?:\.\d+)?),\s*(\d(?:\.\d+))?\)\s*', s).groups()
>>> float(a)*float(b)
15.700000000000001

regex101 demo: https://regex101.com/r/O3bSwr/1/

Use numbers in a string input, Python 3

3 Answers3