CODEWITHSUNDEEP
python-3.xlistdictionarydeque
Nayan
Nayan

Reputation: 39

Deque appending dictionary vs Deque(dictionary) in Python

Try to get my head around adding dictionary to a deque .

Take this example:

from collections import deque
graph={}
graph['key']=['value_1','value_2','value_3']
implement_first=deque()
implement_second=deque(graph['key'])
implement_first.append(graph['key'])

and If I print:

    print(implement_first)
    print(implement_first.popleft())

I get this deque([['value_1', 'value_2', 'value_3']]) and ['value_1', 'value_2', 'value_3']

and If I print:

print(implement_second)
print(implement_second.popleft())

I get this : deque(['value_1', 'value_2', 'value_3']) and value_1

So what is going on here ? why am I getting list of list for implement_first.append(graph['key']) and what is this implementation implement_second=deque(graph['key']) does?

Upvotes: 1

Views: 1510

Answers (1)

user2390182
user2390182

Reputation: 73490

The following 2 are not equivalent

d1 = deque(x)

d2 = deque()
d2.append(x)

The deque constructor takes an iterable and appends all its elements. So the following 2 would be the same

d1 = deque(x)

d2 = deque()
for y in x:
    d2.append(y)

Yours does not raise any errors because graph["key"] is a list (an iterable) which can be both turned into a deque and be an element of a deque.

Upvotes: 3

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