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
– vallentin, Commented Apr 11, 2017 at 8:51
@Vallentin Im trying to make a shape calculator, I want user enter the shape name and numbers like this — DarkSuniuM
– DarkSuniuM, Commented Apr 11, 2017 at 8:55
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
– Elmar Peise, Commented Apr 11, 2017 at 9:00

Community · Accepted Answer · 2017-05-23 12:10:22Z

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, 2017 at 12:10

CommunityBot

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answered Apr 11, 2017 at 9:06

Abhishek J

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2 Comments

DarkSuniuM Over a year ago

Thanks alot, It works good, Can u give me a resource about this part ? => [s.find("(")+1:s.find(")")]

Abhishek J Over a year ago

@AlirezaAyinMehr Your welcome and check the edit and the link I attached..

spadarian · Accepted Answer · 2017-04-11 09:06:37Z

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, 2017 at 9:06

answered Apr 11, 2017 at 8:58

spadarian

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3 Comments

Piotr Pęczek Over a year ago

I would parse the statement, but not search for integers

DarkSuniuM Over a year ago

It works, can u explain me that ('\\d+[.]*\\d*', input_) ??

spadarian Over a year ago

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 ()

timgeb · Accepted Answer · 2017-04-11 09:07:40Z

1

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/

answered Apr 11, 2017 at 9:07

timgeb

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