CODEWITHSUNDEEP
pythonstring
terrabl
terrabl

Reputation: 922

Splitting a string and adding the digits inside of the string

How would I go about splitting a string up and then adding up the integers inside, with the code below I am able to add up single integers, but if I get a string like "a12b34" I should be able to do 12 + 34 not 1+2+3+4 like the code below does. I am able to do this in C but I do not know how to 100% do it in python. 

strTest = str(raw_input("Enter an alphanumeric string: "))
total = 0
for ch in strTest:
    if ch.isdigit() == True:
        total = total + int(ch)
print total

Upvotes: 0

Views: 957

Answers (1)

Iron Fist
Iron Fist

Reputation: 10951

User re.findall to extract all digits, convert them to integer and then sum the results

>>> import re
>>> s = 'a12b34'
>>> total = sum(map(int,re.findall(r'-?\d+', s))) # -? is to cover negative values
46

This is valid only if you have integers

EDIT:

For general cases, where you might have float number as well, consider the following:

>>> s = 'a12b32c12.0d11.455'
>>> sum(map(float, re.findall(r'-?\d+\.?\d+', s)))
67.455
>>> s = 'a12b-32c12.0d-11.455'
>>> sum(map(float, re.findall(r'-?\d+\.?\d+', s)))
-19.455

EDIT2:

So what's happening:

1 - import re will import and load re module, which is a module used to extract complex string format based on the provided pattern. More details here

2 - re.findall will return all matching string in s with the provided pattern r'-?\d+\d.>\d+'

3 - The pattern r'-?\d+\d.>\d+ breakdown (which can be found here):

enter image description here

4 - Now, re.findall will return a list of all matches:

>>> s = 'a12b-32c12.0d11.455'
>>> re.findall(r'-?\d+\.?\d+', s)
['12', '-32', '12.0', '11.455']

5 - map will convert each element from this list from string into float returning a generator:

>>> map(float, re.findall(r'-?\d+\.?\d+', s))
<map object at 0x0000000003873470>
>>> list(map(float, re.findall(r'-?\d+\.?\d+', s)))
[12.0, -32.0, 12.0, -11.455]

6 - Passing the result of map to sum will sum all elements to their total:

>>> sum([12.0, -32.0, 12.0, -11.455])
-19.455

Upvotes: 3

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