如何在Python中打印字典的键？

Question

Suppose I have a dictionary:

dictionary1 = {'test':'output','test2':'output2'}

How would I be able to print the key, test , on the screen?

I only want one of the keys at a time, not all of them.

By the way, not literally, by doing print('test') , I mean how do you print the key of any dictionary?

Like is there something like this:

#pseudocode
x = dictionary1.keys()[0]
>>> print(x)
'test'

I do not want to sort the dictionary that I'm actually using in my program.

Answer 1

A dictionary may have any number of keys, 0+. To print them all (if any) in sorted order, you could

for key in sorted(dictionary1):
    print(key)

If you don't care about the order (ie you're fine with a random-looking order), remove the sorted call.

If you want to be selective (eg only print keys that are sequences of length 4, so that in your example test would be printed but test2 wouldn't):

for key in sorted(dictionary1):
    try:
        if len(key) == 4:
            print(key)
    except TypeError:
        pass

If you want to print only one such key, add a break after the print .

There are at least 347 other things you could mean by your extremely vague question, but I tried to field the ones that seem most likely... if that's not enough for you, edit your question to make it much more precise!-)

Added: the edit only said the OP wants to print only one key and do no sorting, so it remains a mystery how that one key is to be picked (I suspect there's a misunderstanding -- as if dict keys had a specific order, which of course in Python they don't, and the OP wants "the first one", which just can't be pinned down -- OrderedDict is a very different [and alas inevitably slower] beast, but dict s what the OP's showing).

So if the goal is to print "any one key, no matter which one" (and it is known that thedict is not empty):

print(next(iter(thedict)))

is the simplest, most direct way -- a dict is iterable, yielding its keys in arbitrary order; iter returns an iterator on its iterable argument; and next returns the first (first in arbitrary order means an arbitrary one of course) item of its iterator argument.

If it's possible for thedict to be empty, and nothing must be printed in that case, just add a guard:

if thedict: print(next(iter(thedict)))

This will print nothing for an empty dictionary, the only key for a dictionary with length 1, an arbitrary key for a dictionary with length greater than 1.

Answer 2

If you're trying to find a key associated with a specific value you can do

keys = [key for key in d if d[key] == value]
print(keys)