Python: Can one create new variable names from a list of strings?

Question

I'm new to python, so I don't know if this is possible. I'm trying to create a list of variable names from a list of strings so I can then assign values to the newly created variables.

I saw another similar question, but there was already a dict pays of keys and values.

Here's my code:

def handy(self):
    a = raw_input('How many hands? ')
    for i in range(int(a)):
        h = "hand" + str(i+ 1)
            self.list_of_hands.append(h)
            # would like to create variable names from self.list_of_hands
            # something like "hand1 = self.do_something(i)"
            print h
    print self.list_of_hands

Given some of the answers, i'm adding the following comment: I'm going to then assign dicts to each variable. So, can I create a dictionary of dictionaries?

http://stackoverflow.com/questions/295058/convert-string-to-preexisting-variable-names http://stackoverflow.com/questions/2553354/how-to-get-a-variable-name-as-a-string-in-python http://stackoverflow.com/questions/6122816/how-to-convert-string-to-variable-name — avasal, Aug 22 '12 at 05:21
@avasal At the risk of sounding very thick, I don't understand how your examples apply here. Any chance you could apply them to what I'm trying to do? many thanks. — DBWeinstein, Aug 22 '12 at 05:40
@dwstein your trying to dynamically create variable names. The solutions mentioned in avasal's post say that you are probably better off using a dictionary with the variable names as keys, or as a list since the names are simply `hand + ` — Snakes and Coffee, Aug 22 '12 at 06:58

verdesmarald · Accepted Answer · 2012-08-22T05:39:47.023

Why don't you just construct a dictionary using the strings as keys?

>>> class test():
    def handy(self):
        a = raw_input('How many hands? ')
        d = { "hand" + str(i + 1) : self.do_something(i) for i in range(int(a)) }

        keys = d.keys()
        keys.sort()
        for x in keys:
            print x, '=', d[x]

    def do_something(self, i):
        return "something " + str(i)

>>> test().handy()
How many hands? 4
hand1 = something 0
hand2 = something 1
hand3 = something 2
hand4 = something 3

Edit: You updated the question to ask if you can store a dictionary as a value in a dictionary. Yes, you can:

>>> d = { i : { j : str(i) + str(j) for j in range(5) } for i in range(5) }
>>> d[1][2]
'12'
>>> d[4][1]
'41'
>>> d[2]
{0: '20', 1: '21', 2: '22', 3: '23', 4: '24'}
>> d[5] = { 1 : '51' }
>> d[5][1]
'51'

score 2 · Answer 2 · answered Aug 22 '12 at 05:28

2

If you ever have multiple variables that only differ by a number at the end (hand1, hand2, etc.), you need a container.

I think a dictionary would work best:

self.hands = {}
self.hands[h] = self.do_something(i)

You can access the individual keys in the dictionary easily:

self.hands['hand1']

answered Aug 22 '12 at 05:28

Blender

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Thanks! But, will this work if I'm then going to assign a dict to each name? I guess I'm asking if you can create a dictionary of dictionaries? – DBWeinstein Aug 22 '12 at 05:32
3

Dictionaries are hashable so it will work. – Blender Aug 22 '12 at 05:34

score 2 · Answer 3 · answered Aug 22 '12 at 06:23

2

h = "hand" + str(i+ 1)
vars()[h] = do_something(i)

Now you can call hand1 to call do_something()

answered Aug 22 '12 at 06:23

thavan

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Python: Can one create new variable names from a list of strings?

3 Answers3