How to iterate through dict in random order in Python?

Question

How can I iterate through all items of a dictionary in a random order? I mean something random.shuffle, but for a dictionary.

Answer 1

import random

def main():

    CORRECT = 0

    capitals = {'Alabama': 'Montgomery', 'Alaska': 'Juneau',
        'Arizona': 'Phoenix', 'Arkansas': 'Little Rock'} #etc... you get the idea of a dictionary

    allstates = list(capitals.keys()) #creates a variable name and list of the dictionary items
    random.shuffle(allstates) #shuffles the variable

    for a in allstates: #searches the variable name for parameter
        studentinput = input('What is the capital of '+a+'? ')
        if studentinput.upper() == capitals[a].upper():
            CORRECT += 1
main()

Answer 2

As Charles Brunet have already said that the dictionary is random arrangement of key value pairs. But to make it really random you will be using random module. I have written a function which will shuffle all the keys and so while you are iterating through it you will be iterating randomly. You can understand more clearly by seeing the code:

def shuffle(q):
    """
    This function is for shuffling 
    the dictionary elements.
    """
    selected_keys = []
    i = 0
    while i < len(q):
        current_selection = random.choice(q.keys())
        if current_selection not in selected_keys:
            selected_keys.append(current_selection)
            i = i+1
    return selected_keys

Now when you call the function just pass the parameter(the name of the dictionary you want to shuffle) and you will get a list of keys which are shuffled. Finally you can create a loop for the length of the list and use name_of_dictionary[key] to get the value.

Answer 3

A dict is an unordered set of key-value pairs. When you iterate a dict, it is effectively random. But to explicitly randomize the sequence of key-value pairs, you need to work with a different object that is ordered, like a list. dict.items(), dict.keys(), and dict.values() each return lists, which can be shuffled.

items=d.items() # List of tuples
random.shuffle(items)
for key, value in items:
    print key, value

keys=d.keys() # List of keys
random.shuffle(keys)
for key in keys:
    print key, d[key]

Or, if you don't care about the keys:

values=d.values() # List of values
random.shuffle(values) # Shuffles in-place
for value in values:
    print value

You can also "sort by random":

for key, value in sorted(d.items(), key=lambda x: random.random()):
    print key, value

Answer 4

You can't. Get the list of keys with .keys(), shuffle them, then iterate through the list while indexing the original dict.

Or use .items(), and shuffle and iterate that.

Answer 5

I wanted a quick way for stepping through a shuffled list, so I wrote a generator:

def shuffled(lis):
    for index in random.sample(range(len(lis)), len(lis)):
        yield lis[index]

Now I can step through my dictionary d like so:

for item in shuffled(list(d.values())):
    print(item)

or if you want to skip creating a new function, here is a 2-liner:

for item in random.sample(list(d.values()), len(d)):
    print(item)