how to fill a dict with None for all keys (given in a list) in Python 3.3 [duplicate]

Question

For a writerow of a csv.DictWriter, I need to fill a (part of a) dictionary to be empty. I found no immediate solution for it. Is there one?

Like with

fieldnames = ['first','last']

Pseudocode

row = fieldnames.fill(None)

Result

print(row)
['first':None,'last':None]

So that

destination.writerow(row)

results in

,

Answer 1

This is really a natural for the built-in dict method fromkeys:

>>> dict.fromkeys('abcd',None)
{'a': None, 'c': None, 'b': None, 'd': None}
>>> dict.fromkeys(['first','last'],None)
{'last': None, 'first': None}

No need for a dict comprehension (2.7+) or a list comprehension at all.