Python Applying map function to sub list

Question

I have an array holding another object items :

myarray=[]
myarray.append((1,2,3))
myarray.append((4,5,6))

how can I apply a map function to the last 2 columns of the list somethign like

def inc(x):
  return x+1

then

myarray map (inc) # only to the last 2 columns (2,3) and (5,6)

in short I want to transform the data structure from

((1,2,3))
((4,5,6))

to

((1,3,4))
((4,6,7))

thanks

EDIT: just so others can benfit from this I wrote to functions based on @alef response

def format_sub_list(_list,i):
  return [[y if i < len(x)-i else inc(y)
  for i, y in enumerate(x)]
  for x in _list]

or

def format_sub_list2(_list,sublist):
  return [[y if i in (sublist) else inc(y)
  for i, y in enumerate(x)]
  for x in _list]

Shall the result be just the return values of the inc or shall it also contain the values which have not been given to inc? — Alfe
– Alfe, Commented May 8, 2013 at 19:51

Alfe · Accepted Answer · 2013-05-08 20:01:28Z

1

[[y if i < len(x)-2 else inc(y)
  for i, y in enumerate(x)]
  for x in my_array]

edited May 8, 2013 at 20:01

answered May 8, 2013 at 19:55

Alfe

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1 Comment

CruncherBigData Over a year ago

This is a good answer. I modified it so that r=[[y if i in (1,4) else inc(y) for i, y in enumerate(x)] for x in myarray] , this way it will be more flexiable in terms of excepting various conditions

Carl Groner · Accepted Answer · 2013-05-08 20:15:13Z

1

l[:-2] + tuple(map(inc, l[-2:]))

edited May 8, 2013 at 20:15

answered May 8, 2013 at 19:59

Carl Groner

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4 Comments

Alfe Over a year ago

Yeah, but I guessed that the number 2 would not be constant. Also the number of columns might be variable. I feel your answer is based on assuming too much.

CruncherBigData Over a year ago

Thanks for the reply. I agree with Alfe, this is somewhat hard coded.

CruncherBigData Over a year ago

I agree , it is more flexible

Alfe Over a year ago

The adding needs to be done for each tuple (being an element of the array).

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