To find duplicates in a python list, why doesn't this logic work? -

while aware best , simplest method find duplicates in list using collections.counter, wish know following logic fail.

def uniquenumbercheck(listarg):     in range(2,len(listarg)):         j in range(1,i-1):             if(listarg[i]==listarg[j]):                 print("duplicate value appeared : "+str(listarg[i]))                 return     print("all entered values unique. ") 

the program running failed display correct output.could not figure out mistake.for example input of 1,1,0 integers list, says unique.

off-by-one error. in python, indexes start @ 0, not 1. so,

for in range(2, len(listarg)):     j in range(1, - 1): 

should be:

for in range(1, len(listarg)):     j in range(0, i): 

also, range(1, len(listarg)) can written range(len(listarg)).