This is a useful bit of code for removing whitespace from a list of strings. For example, if you split a string, there might be superfluous whitespace.
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# striplist.py # Take a list of string objects and return the same list # stripped of extra whitespace. def striplist(l): return([x.strip() for x in l]) # This may look a bit more elegant, but it is significantly slower than # striplist(). This may be dur to the fact that it's using the string.strip() # method. from string import strip def inefficient(l): return(map(strip, l)) del strip # Another version of inefficient() using builtin strip() def inefficient_as_well(l): return(map(lambda x: x.strip(), l)) # This is only slightly slower than or comparable to striplist() def comparable(l) for x in xrange(len(l)): l[x] = l[x].strip() return(l) # This is also on the same order as both comparabale() & striplist() def comparable_as_well(l) tmp =  for x in len(l): tmp.append(x.strip()) return(tmp) # An example of a class that would have the strip method. It inherits # everything from "list", and adds a method, .strip() # This is slower than striplist() class StrippableList(list): def __init__(self,l=): list.__init__(self,l) def strip(self,char=None): return(StrippableList([x.strip(char) for x in self]))
This is a function that I use quite a bit, and so far is the fastest implementation I could come up with. Since Python has a high overhead for function calls, the most efficient way is to strip the elements you need from within your code. In fact, it may be faster to implement the [x.strip() for x in l] idiom right in your code.
My reason for getting into this was because I was having a huge problem with the speed of some of my code. Using profile showed me that the function calls I had going out to strip the list of strings was having a big impact on the speed of execution. Simple functions can have a big impact!
An alternative might be to add a .strip() method to the list class -- this might improve speed (by pushing the code into C). The class StrippableList() is an example in python (since I'm no C coder). It's slower than striplist(), however.