working with dict : incrementing dict dynamically

[John Gordon]

In <mailman.3191.1363015388.2939.python-list at python.org> inshu chauhan <insideshoes at gmail.com> writes:

> --14dae93408ffe4594104d7a7bf0c
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> I am trying to create a dictionary with a key and its values seraching from
> a data set. But something is going wrong. This is the first time I am
> working with dicts.

> My code is :

> import cv
> def Computesegclass(segimage):
>     num_pixel = 0
>         for y in xrange(0, segimage.height):
>         for x in xrange(0, segimage.width):

>             if segimage[y,x] == (0.0, 0.0, 0.0):
>                 continue
>             else:
>                 color = segimage[y,x]
>                 blue = color[0]
>                 green = color[1]
>                 red = color[2]
>                 region_num = blue + 256 * green + 65536 * red
>                 print region_num
>                 segments = dict({region_num : num_pixel})

You're creating a new segments dictionary for each pixel, overwriting
the previous one.  Instead, you probably want to create an empty dictionary
at the top of your function.

>                 if region_num == region_num:

This if statement will always evaluate true, because you're comparing
region_num to itself.

>                     num_pixel = +1

This doesn't store the value of num_pixel in the dictionary.  You probably
want to do this instead:

    segments[region_num] += 1

-- 
John Gordon                   A is for Amy, who fell down the stairs
gordon at panix.com              B is for Basil, assaulted by bears
                                -- Edward Gorey, "The Gashlycrumb Tinies"