Can't calculate two values replacing certain sign

Question

How can I add two values replacing / between them? I tried with item.replace("/","+") but it only places the + sign replacing / and does nothing else. For example If i try the logic on 2/1.5 and -3/-4.5, I get 2+1.5 and -3+-4.5.

My intention here is to add the two values replacing / between them and divide it into 2 so that the result becomes 1.875 and -3.75 respectively if I try the logic on (2/1.5 and -3/-4.5).

This is my try so far:

for item in ['2/1.5','-3/-4.5']:
    print(item.replace("/","+"))

What I'm having now:

2+1.5
-3+-4.5

Expected output (adding the two values replacing / with + and then divide result by two):

1.75
-3.75

Thee are strings, and you would have to compile and execute at runtime. It would probably be better to extract the operator, convert the numeric strings to objects of the correct type, then add or divide them. — cdarke, Aug 12 '18 at 08:06
Dive that into 2. I have mentioned it in my post @Agile_Eagle. — SIM, Aug 12 '18 at 08:08

score 3 · Accepted Answer · answered Aug 12 '18 at 08:12

Since / is only a separator, you don't really need to replace it with +, but use it with split, and then sum up the parts:

for item in ['2/1.5', '-3/-4.5']:
    result = sum(map(float, item.split('/'))) / 2
    print(result)

or in a more generalized form:

from statistics import mean

for item in ['2/1.5', '-3/-4.5']:
    result = mean(map(float, item.split('/')))
    print(result)

Agile_Eagle · Answer 2 · 2018-08-12T08:14:17.650

1

You can do it using eval like this:

for item in ['2/1.5','-3/-4.5']:
    print((eval(item.replace("/","+")))/2)

edited Aug 12 '18 at 08:14

answered Aug 12 '18 at 08:08

Agile_Eagle

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Did you downvote me, yeah i don't know if `literal_eval` is good, that'a true – U12-Forward Aug 12 '18 at 08:11
I realized for here `literal_eval` is safe: https://stackoverflow.com/questions/4710247/python-3-are-there-any-known-security-holes-in-ast-literal-evalnode-or-string – U12-Forward Aug 12 '18 at 08:20
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`eval` is almost always the worst idea. – DYZ Aug 12 '18 at 08:27

score 1 · Answer 3 · answered Aug 12 '18 at 08:22

1

My answer is not that different from others, except I don't understand why everyone is using lists. A list is not required here because it won't be altered, a tuple is fine and more efficient:

for item in '2/1.5','-3/-4.5':            # Don't need a list here
    num1, num2 = item.split('/')
    print((float(num1) + float(num2)) / 2)

answered Aug 12 '18 at 08:22

cdarke

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I suppose, the OP used the list only as an example. – Daniel Aug 12 '18 at 08:44

score 1 · Answer 4 · answered Aug 12 '18 at 08:25

1

A further elaboration of @daniel's answer:

[sum(map(float, item.split('/'))) / 2 for item in ('2/1.5','-3/-4.5')]

Result:

[1.75, -3.75]

answered Aug 12 '18 at 08:25

DYZ

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score 0 · Answer 5 · edited Mar 24 '21 at 15:43

0

from ast import literal_eval

l = ['2/1.5','-3/-4.5']
print([literal_eval(i.replace('/','+'))/2 for i in l])

edited Mar 24 '21 at 15:43

iacob

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answered Aug 12 '18 at 08:07

U12-Forward

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score 0 · Answer 6 · edited Aug 12 '18 at 08:15

0

You can do it like this(by splitting the strings into two floats):

for item in ['2/1.5','-3/-4.5']:
    itemArray = item.split("/")
    itemResult = float(itemArray[0]) + float(itemArray[1])
    print(itemResult/2)

edited Aug 12 '18 at 08:15

cdarke

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answered Aug 12 '18 at 08:10

Gehan Fernando

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I edited your question because the OP wanted the result to be divided by 2 – Agile_Eagle Aug 12 '18 at 08:12
I edited your question because you are using (correctly) floats not integers. – cdarke Aug 12 '18 at 08:16

Can't calculate two values replacing certain sign

6 Answers6