A magical journey through bullshit.

map-lambda-reduce.py

>>> weight
10
>>> a
[1, 2, 3]

# ok, we have a nice list here. let's apply a map() to see if we can raise the power of all values:

>>> map((lambda x: x**2), a)
[1, 4, 9]

# sweet, it works! ok, now let's try to fold in your example of iterating and incrementing:

>>> map((lambda x: weight += x), a)
  File "<stdin>", line 1
    map((lambda x: weight += x), a)
                           ^
SyntaxError: invalid syntax

# b..but..

>>> what
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
NameError: name 'what' is not defined

# ok, well. maybe `lambda` in Python is not a closure, which would mean it doesn't have access to the surrounding stack frame and all its variables.

>>> map((lambda x: x + weight), a)
[11, 12, 13]

# a;dfkjasdf;lkasjdf ok, it is an actual closure. that's annoying. let's..hm. _how about reduce()_? we know from Lisp that transforms a vector to a scalar..

>>> reduce((lambda x,y: x + y), a)
6

# yay, it works!

>>> exit
'Use Ctrl-Z plus Return to exit.'

# ok, you can just fuck right along now.