Colin J. Williams wrote:
John Salerno wrote:
I posted this code last night in response to another thread, and after
I posted it I got to wondering if I had misused the list
comprehension. Here's the two examples:
Example 1:
--------------------
def compress(s):
new = []
for c in s:
if c not in new:
new.append(c)
return ''.join(new)
----------------------
Example 2:
------------------------
def compress(s):
new = []
[new.append(c) for c in s if c not in new]
return ''.join(new)
--------------------------
In example 1, the intention to make an in-place change is explicit,
and it's being used as everyone expects it to be used. In example 2,
however, I began to think this might be an abuse of list
comprehensions, because I'm not assigning the result to anything (nor
am I even using the result in any way).
What does everyone think about this? Should list comprehensions be
used this way, or should they only be used to actually create a new
list that will then be assigned to a variable/returned/etc.?
Alternative ways of of looking at the problem are:
# compress.py
import sets
def compress(s):
new = []
[new.append(c) for c in s if c not in new]
return ''.join(new)
def compress1(s):
new= []
d= dict(zip(s, len(s)*[[]]))
return d.keys()
def compress2(st):
s= sets.Set(st)
return s
if __name__ == "__main__":
s= 'In example 1, the intention to make an in-place change is
explicit, and it is'
print (compress(s))
print (compress1(s))
print (compress2(s))
Results:
In exampl1,thiok-cgsd
['a', ' ', 'c', 'e', 'i', 'g', 'I', 'h', 'k', '-', 'm', 'l', 'o', 'n',
'1', 'p', 's', 't', 'x', ',', 'd']
Set(['a', ' ', 'c', 'e', 'i', 'g', 'I', 'h', 'k', '-', 'm', 'l', 'o',
'n', '1', 'p', 's', 't', 'x', ',', 'd'])
Colin W.
I should have read all the responses
before responding!
Paul McGuire had already suggested a set
approach
Colin W.
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