Greetings Tutors,
I am having some difficulties with the concept of functions which can
accept an unnamed number of arguments. Specifically, when trying to
write a function that deals with an unnamed number of dictionaries. I
want to be able to merge any number of dictionaries, while preserving
the values (ie. cannot use update()).
~I would appreciate any help that can point in me in the right
direction, without directly providing me the answer.~
I understand how to accomplish this task with named arguments:
def mergedicts(firstdict, seconddict):
'''merges two dictionaries into a single dictionary, and converts
duplicate key values to a list'''
newdict = firstdict.copy()
for key in seconddict.keys():
if key in firstdict.keys():
newdict[key] = firstdict[key], seconddict[key]
newdict[key] = list(newdict[key])
else:
newdict[key] = seconddict[key]
return newdict
dict1 = {'1':'a','2':'b','3':'c'}
dict2 = {'4':'d','5':'e','6':'f','1':'g'}
somedicts1 = mergedicts(dict1,dict2)
print somedicts1
#returns: {'1': ['a', 'g'], '3': 'c', '2': 'b', '5': 'e', '4': 'd', '6':
'f'}
I also think I understand how to use unnamed arguments to merge lists:
def mergelists(*somelists):
'''merges multiple lists into a single list and consolidates lists
elements'''
mergedict = {}
for element in somelists:
for unique in element:
mergedict[unique] = 1
combolist = mergedict.keys()
return combolist
Where I am getting hung up is that, if I do this with unnamed arguments
for dictionaries:
def mergedicts(*somedicts):
I get an: AttributeError: 'tuple' object has no attribute 'keys'
However, I run into the same problem when trying with one named, and
unnamed.
def mergedicts2(firstdict,*somedicts):
'''merges any number of dictionaries into a single dictionary, and
converts duplicate key values to a list'''
merged = firstdict.copy()
for key in somedicts.keys():
if key in merged.keys():
merged[key] = merged[key], somedicts[key]
merged[key] = list(merged[key])
else:
merged[key] = somedicts[key]
return merged
Based on my understanding of how unnamed arguments work in functions: I
think the dictionaries are being converted into a tuple of all of the
dictionary values, and I cannot make a working copy of the first
dictionary passed to the function, with the named example. Should I then
unpack the resulting tuple into corresponding first,second,third...
dictionaries for further processing?
I am also wondering if this is even the right approach? Can this be done
with only unnamed arguments, or do I at least need to name the first
argument for the first reference dictionary, and then use an *unnamed
for each additional dictionary?
Thanks for any pointers,
Colin
--
"f u cn rd ths, u cn gt a gd jb n cmptr prgrmmng." - Anonymous
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