Append dict items to a list with a single line for loop

Question

I have a list

lst = []

I have dict entries

a= {'a':1,'b':2}

I wish to write a for loop in a comprehension manner filling the list. What I have tried is

lst.append(k,v) for (k,v) in a.items()

I need to then update the dict as

a = {'c':3, 'd':4}

Then again update the list lst.

Which adds the tuples as [('a',1)('b',2)('c',3)('d',4)] What is the right way to iterate through a dict and fill the list?

Answer 1

This is what the syntax for a list comprehension is and should do what you're looking for:

lst = [(k,v) for k,v in a.items()]

In general list comprehension works like this:

someList = [doSomething(x) for x in somethingYouCanIterate]

OUTPUT

>>> lst
[('a', 1), ('b', 2)]

P.S. Apart from the question asked, you can also get what you're trying to do without list comprehension by simply calling :

lst = a.items()

this will again give you a list of tuples of (key, value) pairs of the dictionary items.

EDIT

After your updated question, since you're updating the dictionary and want the key value pairs in a list, you should do it like:

a= {'a':1,'b':2}
oldA = a.copy()
#after performing some operation
a = {'c':3, 'd':4}
oldA.update(a)
# when all your updates on a is done
lst = oldA.items() #or [(k,v) for k,v in oldA.items()]
# or instead of updating a and maintaining a copy
# you can simply update it like : a.update({'c':3, 'd':4}) instead of a = {'c':3, 'd':4}