I understand this toy example:
lines = "this is a group\nof lines of\nwords"
def getlength(w): return len(w)
s = map(getlength, [word for ln in lines.split() for word in ln.splitlines()])
(now s is [4, 2, 1, 5, 2, 5, 2, 5])
My question is whether there's any compact way to combine function calls, like this (which doesn't work):
lines = "this is a group\nof lines of\nwords"
def getlength(w): return len(w)
def timestwo(x): return x * 2
s = map(timestwo(getlength), [word for ln in lines.split() for word in ln.splitlines()])
(Under the WingIDE I get this traceback:
"/Applications/WingIDE-Professional-2.0.2/WingIDE.app/Contents/MacOS/ src/debug/server/_sandbox.py", line 1, in ?
# Used internally for debug sandbox under external interpreter
File "/Applications/WingIDE-Professional-2.0.2/WingIDE.app/Contents/MacOS/ src/debug/server/_sandbox.py", line 1, in addone
# Used internally for debug sandbox under external interpreter
TypeError: unsupported operand type(s) for +: 'function' and 'int'
)
I hope the question is clear enough. I have a feeling I'm ignoring a simple technique . . .
Charles Hartman
Hi Charles,
perhaps I'm distracted by the `toy' nature of the examples, but maybe this will help:
>>> lines = "this is a group\nof lines of\nwords" >>> [len(x) for x in lines.split()] [4, 2, 1, 5, 2, 5, 2, 5] >>> [len(x)*2 for x in lines.split()] [8, 4, 2, 10, 4, 10, 4, 10] >>> def some_arbitrary_function(y): ... return ( (y * 42) - 19 ) % 12 ... >>> [some_arbitrary_function(len(x)) for x in lines.split()] [5, 5, 11, 11, 5, 11, 5, 11] >>>
I could be missing some edge cases, but it seems to me that if you have list comps you don't really need map, filter, and the like. The map portion can be done by nested function applications in the list comp itself.
Best,
Brian vdB -- http://mail.python.org/mailman/listinfo/python-list
