Monday, April 21, 2014

map reduce filter zip ...

Importance -- these handful of functions are the core FP features in Python, according to http://www.ibm.com/developerworks/linux/library/l-prog/index.html?ca=drs-

I feel it's good to tackle the family members one by one, as a group. I believe each has some counterpart in either perl, C++, java and most likely in c#, so we can just list one counterpart to help us grasp each.

Bear in mind how common/uncommon each function is. Don't overspend yourself on the wrong thing.

Don't care about list vs tuple for now! Don't care about advanced usages. Just grasp one typical usage of each.

http://www.lleess.com/2013/07/python-built-in-function-map-reduce-zip.html is concise.

--filter() = grep in perl

filter(function, sequence) -> sequence

>>> filter(lambda d: d != 'a', 'abcd') 
'bcd'

--map() = map in perl

>>> map(lambda a: a+1, [1,2,3,4] )
[2, 3, 4, 5]

--reduce = Aggregate() in c#
reduce(function, sequence [, initial]) -> value

>>> reduce(lambda x, y: x+y, range(0,10), 10)
55

--zip is less common

--apply() is deprecated

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