My very first python program, need help

Discussion in 'Python' started by WP, Aug 10, 2008.

  1. WP

    WP Guest

    Hello, below is my very first python program. I have some questions
    regarding it and would like comments in general. I won't be able to get
    my hands on a good python book until tomorrow at the earliest. The
    program takes a string and sums all numbers inside it. I'm testing with
    the following string: "123xx,22! p1" which should yield a sum of 123 +
    22 + 1 = 146. My solution to this exercise was to write a function that
    takes a string and splits it into a list of numbers and then I will sum
    up the numbers in the list. In fact, I wrote two versions of this
    function: One uses a for loop to replace all characters that is not a
    digit and not a space with a space. That should leave me with the
    numbers intact and with only spaces separating these numbers. Then I
    call split to get a list of numbers (here I discovered I must not use a
    sep equal to ' ' or the returned list would contain empty strings as
    well). This is calculate_sum_1() and look at the comment in the code to
    see what worries me there. The second one uses regular expressions and
    the problem I have with that is that I get a list of containing not just
    the numbers but empty strings as well. I'm working around that in my
    loop that sums the numbers but it would be better to not have these
    empty string in the list in the first place. Here's the code:

    import re

    def calculate_sum_1(str):
    for c in str:
    if c.isdigit() == False and c != ' ':
    # That we assign to the variable we're looping over worries
    str = str.replace(c, ' ')

    mylist = str.split()

    print "(for loop version) mylist after replace() and split() = ",

    sum = 0

    for item in mylist:
    sum += long(item)

    return sum

    def calculate_sum_2(str):
    #print "In replace_nondigits_2(), str = ", str
    p = re.compile('[^0-9]')

    mylist = p.split(str)

    print "(regex version) mylist after calling split(): ", mylist

    sum = 0

    for item in mylist:
    if item.isdigit():
    sum += long(item)

    return sum

    str = "123xx,22! p1" # Sum = 123 + 22 + 1 = 146

    print "str = ", str

    print "calculate_sum_1(str): %d" % calculate_sum_1(str)
    print "calculate_sum_2(str): %d" % calculate_sum_2(str)

    The output when run is:
    str = 123xx,22! p1
    (for loop version) mylist after replace() and split() = ['123', '22', '1']
    calculate_sum_1(str): 146
    (regex version) mylist after calling split(): ['123', '', '', '22', '',
    '', '1']
    calculate_sum_2(str): 146

    Hope I made some sense and thanks for reading!

    - Eric (WP)
    WP, Aug 10, 2008
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  2. WP

    WP Guest

    Wojtek Walczak wrote:
    Thanks for all your help. I've incorporated your suggestions and moved
    on to my next program. See new thread. :)

    - Eric (WP)
    WP, Aug 10, 2008
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