Python: Extracting values from list of values

Question

I'm trying to write a function that consumes a list of keycode values, and produces a string corresponding to these values. Each keycode contains 2 values, the first corresponding to a number of a phone and the second corresponding to a certain value from the list of values that define each number. I'm having trouble extracting these values. This is the list of values that correspond with each number:

0 == [" "]
1 == [".", ",", "?"]
2 == ["a", "b", "c"]
3 == ["d", "e", "f"]
4 == ["g", "h", "i"]
5 == ["j", "k", "l"]
6 == ["m", "n", "o"]
7 == ["p", "q", "r", "s"]
8 == ["t", "u", "v"]
9 == ["w", "x", "y", "z"]`

If the list of keyed values that I'm consuming is keypresses: [[6,3], [0, 1], [5, 2]] How can I extract certain values from the definitions above? I'm thinking about using .join(list) and map for once I have the values extracted.

a/ make a dict or an array out of the data you have. typically, [[' '], ['.',',','?'], ...]or {'0': [' '], ...}. b/ access that data using the input you have : ''.join(values[key][cnt - 1] for (key, cnt) in keypresses) — njzk2
– njzk2, Commented Jun 30, 2015 at 2:40

Óscar López · Accepted Answer · 2015-06-30 02:49:45Z

1

Try using a list of lists, like this:

lsts = [[" "],
        [".", ",", "?"],
        ["a", "b", "c"],
        ["d", "e", "f"],
        ["g", "h", "i"],
        ["j", "k", "l"],
        ["m", "n", "o"],
        ["p", "q", "r", "s"],
        ["t", "u", "v"],
        ["w", "x", "y", "z"]]

Now you can access each sublist by its index:

lsts[1]
=> [".", ",", "?"]

And each element by both of its indexes:

lsts[1][2]
=> "?"

Now it's easy to extract values from a list of key presses, like those shown in the question and then join them:

keypresses = [[6, 3], [0, 1], [5, 2]]
''.join(lsts[i][j-1] for i, j in keypresses)
=> "n k"

Notice that the indexes start from zero, so I had to subtract one unit from the sample key presses given in the question.

edited Jun 30, 2015 at 2:49

answered Jun 30, 2015 at 2:42

Óscar López

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1 Comment

Shagun Chhikara Over a year ago

Thank you for a solution thats easy to understand and works perfectly!!

Red Shift · Accepted Answer · 2015-06-30 02:43:28Z

1

This should do what your looking for.

def key_pressed(key, character):
    """
    :param key: index of keyboard button
    :param character: desired character represented by key
    :return: requested character
    """
    lookup = [[" "],
              [".", ",", "?"],
              ["a", "b", "c"],
              ["d", "e", "f"],
              ["g", "h", "i"],
              ["j", "k", "l"],
              ["m", "n", "o"],
              ["p", "q", "r", "s"],
              ["t", "u", "v"],
              ["w", "x", "y", "z"]]

    return lookup[key][character]


print(key_pressed(6, 2))
print(key_pressed(1, 2))
print(key_pressed(5, 1))

Output:

o
?
k

answered Jun 30, 2015 at 2:43

Red Shift

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Comments

Geotob · Accepted Answer · 2015-06-30 02:41:02Z

0

I would suggest you define a dictionary that holds the numbers and corresponding values like so:

keyvalmap = {0: [" "], 1: [".", ",", "?"]} #and so on...

Then iterate over keypresses:

for key, times in keypresses:
    print keyvalmal[key][times-1] # or whatever you want to do

answered Jun 30, 2015 at 2:41

Geotob

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