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I have a problem that is simple but I’m not getting the solution.
I have a list of tuples, for example:
lista = [('x',2,3),('y',4,5),('x',6,7),('z',8,9)]
What I want is for him to tell me how many times x,y and z on that list. In this case the x appears 2 times and the y and z appear 1 time, soon should return me a list with [2,1,1].
And I wanted to settle this with map or reduce.
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Word count is the basic example of map/reduce. In this case, just adapt the map step and implement the traditional reduce. Follow an example for mapper:
mapper.py
lista = [('x',2,3),('y',4,5),('x',6,7),('z',8,9)]
for i in lista:
print '%s\t%s' % (i[0], '1')
Here is a full example documentation: http://www.michael-noll.com/tutorials/writing-an-hadoop-mapreduce-program-in-python/
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You can use the excellent Counter of collections:
from collections import Counter
lista_contagens = Counter(map(lambda: x, x[0], lista))
# Isto imprime as contagens
print(lista_contagens.values())
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the
xinside the lambda represents what? Tells me it is not set– CSAnimor
I already solved it, it was :
lista_contagens = Counter(map(lambda x: x[0], lista))but this does not return me the list as I wanted:[2,1,1]– CSAnimor
I updated the answer.
– Leonel Sanches da Silva
That’s right, thank you!
– CSAnimor