dictionary - Merging two dicts in python with no duplication permitted -

this question differs similar dictionary merge questions in conflicting duplicates should fail, or return false. other solutions use precedence rule decide how manage when 1 key might mapped 2 different variables.

how merge 2 dicts efficiently in python. example, consider:

d1 = {'x': 'a', 'y': 'b', 'z': 'c'} d2 = {'z': 'c', 'w': 'r'} d3 = {'z': 'd', 'w': 'r'} 

so, result of merging dictionary 1 , 2 be

{'x': 'a', 'y': 'b', 'z': 'c', 'w': 'r'} 

but merge of 1 , 3 or 2 , 3 should fail because z has conflict.

my solution is:

def merge_dicts(d1,d2):    k1=d1.keys()    k2=d2.keys()    unified_dict=dict()    k in k1:        # in second dictionary       if k in k2:          pt=d2[k]  #pt stands 'plain text'          # if lookup contradiction, return empty dictionary          #  don't bother partial results          if pt!=d1[k]:              return dict()          else:              unified_dict[k]=d1[k]  # safe: key consistent       else:           unified_dict[k]=d1[k] # safe:  no key in k2  # rest # resolved intersection issues set difference    k in d2.keys():       if k not in d1.keys():           unified_dict[k]=d2[k]     return unified_dict 

any improvements?

use dictionary views here; let treat dictionary keys sets:

def merge_dicts(d1, d2):     try:         # python 2         intersection = d1.viewkeys() & d2     except attributeerror:         intersection = d1.keys() & d2      if any(d1[shared] != d2[shared] shared in intersection):         return {}  # empty result if there conflicts      # leave rest c code, execute fast merge using dict()     return dict(d1, **d2) 

the above code tests shared keys referencing non-matching values; merge best left dict() function.

i made function work both on python 2 , python 3; if need support 1 or other, remove try..except , replace intersection relevant expression. in python 3 dict.keys() method returns dictionary view default.

you conceivably make one-liner; python 3 version:

def merge_dicts(d1, d2):     return {} if any(d1[k] != d2[k] k in d1.keys() & d2) else dict(d1, **d2) 

demo:

>>> d1 = {'x': 'a', 'y': 'b', 'z': 'c'} >>> d2 = {'z': 'c', 'w': 'r'} >>> d3 = {'z': 'd', 'w': 'r'} >>> merge_dicts(d1, d2) {'y': 'b', 'x': 'a', 'z': 'c', 'w': 'r'} >>> merge_dicts(d1, d3) {} >>> merge_dicts(d2, d3) {}