Python variables as keys to dict

Question

Hello,

Is there an easier way to do this in Python (2.7)?: Note: This isn't anything fancy, like putting all local variables into a dictionary. Just the ones I specify in a list.

apple = 1
banana = 'f'
carrot = 3
fruitdict = {}

# I want to set the key equal to variable name, and value equal to variable value
# is there a more Pythonic way to get {'apple': 1, 'banana': 'f', 'carrot': 3}?

for x in [apple, banana, carrot]:
    fruitdict[x] = x # (Won't work)

Edit: the number assignments were meaningless...changing them.

Answer 1

The globals() function returns a dictionary containing all your global variables.

>>> apple = 1
>>> banana = 'f'
>>> carrot = 3
>>> globals()
{'carrot': 3, 'apple': 1, '__builtins__': <module '__builtin__' (built-in)>, '__name__': '__main__', '__doc__': None, 'banana': 'f'}

There is also a similar function called locals().

I realise this is probably not exactly what you want, but it may provide some insight into how Python provides access to your variables.

Edit: It sounds like your problem may be better solved by simply using a dictionary in the first place:

fruitdict = {}
fruitdict['apple'] = 1
fruitdict['banana'] = 'f'
fruitdict['carrot'] = 3

Answer 2

locals() and globals()?

Answer 3

If you want to bind the locations of the variables themselves, there's this:

>>> apple = 1
>>> banana = 'f'
>>> carrot = 3
>>> fruitdict = {}
>>> fruitdict['apple'] = lambda : apple
>>> fruitdict['banana'] = lambda : banana
>>> fruitdict['carrot'] = lambda : carrot
>>> for k in fruitdict.keys():
...     print k, fruitdict[k]()
... 
carrot 3
apple 1
banana f
>>> apple = 7
>>> for k in fruitdict.keys():
...     print k, fruitdict[k]()
... 
carrot 3
apple 7
banana f

Answer 4

A one-liner is:-

fruitdict = dict(zip(('apple','banana','carrot'), (1,'f', '3'))

Answer 5

for i in ('apple', 'banana', 'carrot'):
    fruitdict[i] = locals()[i]

Answer 6

why you don't do the opposite :

fruitdict = { 
      'apple':1,
      'banana':'f',
      'carrot':3,
}

locals().update(fruitdict)

Update :

don't use the code above check the comment.

by the way why you don't mark the vars that you want to get i don't know maybe like this:

# All the vars that i want to get are followed by _fruit
apple_fruit = 1
carrot_fruit = 'f'

for var in locals():
    if var.endswith('fruit'):
       you_dict.update({var:locals()[var])

Answer 7

Well this is a bit, umm ... non-Pythonic ... ugly ... hackish ...

Here's a snippet of code assuming you want to create a dictionary of all the local variables you create after a specific checkpoint is taken:

checkpoint = [ 'checkpoint' ] + locals().keys()[:]
## Various local assigments here ...
var_keys_since_checkpoint = set(locals().keys()) - set(checkpoint)
new_vars = dict()
for each in var_keys_since_checkpoint:
   new_vars[each] = locals()[each]

Note that we explicitly add the 'checkpoint' key into our capture of the locals().keys() I'm also explicitly taking a slice of that though it shouldn't be necessary in this case since the reference has to be flattened to add it to the [ 'checkpoint' ] list. However, if you were using a variant of this code and tried to shortcut out the ['checkpoint'] + portion (because that key was already inlocals(), for example) ... then, without the [:] slice you could end up with a reference to thelocals().keys()` whose values would change as you added variables.

Offhand I can't think of a way to call something like new_vars.update() with a list of keys to be added/updated. So thefor loop is most portable. I suppose a dictionary comprehension could be used in more recent versions of Python. However that woudl seem to be nothing more than a round of code golf.

Answer 8

This question has practically been answered, but I just wanted to say it was funny that you said

This isn't anything fancy, like putting all local variables into a dictionary.

Because it is actually "fancier"

what you want is:

apple = 1
banana = 'f'
carrot = 3
fruitdict = {}

# I want to set the key equal to variable name, and value equal to variable value
# is there a more Pythonic way to get {'apple': 1, 'banana': 'f', 'carrot': 3}?

names= 'apple banana carrot'.split() # I'm just being lazy for this post
items = globals()                    # or locals()

for name in names:
    fruitdict[name] = items[name]

Honestly, what you are doing is just copying items from one dictionary to another.

(Greg Hewgill practically gave the whole answer, I just made it complete)

...and like people suggested, you should probably be putting these in the dictionary in the first place, but I'll assume that for some reason you can't