Re: suggestions for improving code fragment please
On Thu, Feb 28, 2013 at 12:47 PM, The Night Tripper jkn...@nicorp.co.uk wrote: Hi there I'm being very dumb ... how can I simplify this fragment? if arglist: arglist.pop(0) if arglist: self.myparm1 = arglist.pop(0) if arglist: self.myparm2 = arglist.pop(0) if arglist: self.myparm3 = arglist.pop(0) if arglist: self.parm4 = arglist.pop(0) Perhaps this would work for you: if arglist: defaults = [self.parm1, self.parm2, self.parm3, self.parm4] arglist = arglist[1:] + defaults[len(arglist)-1:] self.parm1, self.parm2, self.parm3, self.parm4 = arglist[:4] -- http://mail.python.org/mailman/listinfo/python-list
Re: suggestions for improving code fragment please
On Thu, Feb 28, 2013 at 2:47 PM, The Night Tripper jkn...@nicorp.co.ukwrote: Hi there I'm being very dumb ... how can I simplify this fragment? i = 0 while arglist: self.myparm[i] = arglist.pop(0) i += 1 if arglist: arglist.pop(0) if arglist: self.myparm1 = arglist.pop(0) if arglist: self.myparm2 = arglist.pop(0) if arglist: self.myparm3 = arglist.pop(0) if arglist: self.parm4 = arglist.pop(0) # ... Thanks J^n -- http://mail.python.org/mailman/listinfo/python-list -- Joel Goldstick http://joelgoldstick.com -- http://mail.python.org/mailman/listinfo/python-list
Re: suggestions for improving code fragment please
On Thursday, February 28, 2013 1:47:12 PM UTC-6, The Night Tripper wrote: I'm being very dumb ... how can I simplify this fragment? if arglist: arglist.pop(0) if arglist: self.myparm1 = arglist.pop(0) if arglist: self.myparm2 = arglist.pop(0) if arglist: self.myparm3 = arglist.pop(0) if arglist: self.parm4 = arglist.pop(0) Depends. If the length of arglist is known you could simply unpack it: a,b,c,d = (1,2,3,4) If the length is unknown, a while loop would do the trick. All you need is to figure out what truth condition to test for on each iteration of the while loop. while truthCondition: #assign variable to value -- http://mail.python.org/mailman/listinfo/python-list
Re: suggestions for improving code fragment please
On 2013-02-28 19:47, The Night Tripper wrote: Hi there I'm being very dumb ... how can I simplify this fragment? if arglist: arglist.pop(0) if arglist: self.myparm1 = arglist.pop(0) if arglist: self.myparm2 = arglist.pop(0) if arglist: self.myparm3 = arglist.pop(0) if arglist: self.parm4 = arglist.pop(0) If they're arbitrarily named attributes of the self, you could do something like for attr in (myparm1, myparm2, myparm3, ...): if arglist: setattr(self, attr, arglist.pop(0)) else: break -tkc -- http://mail.python.org/mailman/listinfo/python-list
Re: suggestions for improving code fragment please
On 2013-02-28 19:47, The Night Tripper wrote: Hi there I'm being very dumb ... how can I simplify this fragment? if arglist: arglist.pop(0) if arglist: self.myparm1 = arglist.pop(0) if arglist: self.myparm2 = arglist.pop(0) if arglist: self.myparm3 = arglist.pop(0) if arglist: self.parm4 = arglist.pop(0) # ... You could just catch the exception: try: arglist.pop(0) self.myparm1 = arglist.pop(0) self.myparm2 = arglist.pop(0) self.myparm3 = arglist.pop(0) self.parm4 = arglist.pop(0) except IndexError: pass -- http://mail.python.org/mailman/listinfo/python-list
Re: suggestions for improving code fragment please
On 02/28/2013 02:47 PM, The Night Tripper wrote: Hi there I'm being very dumb ... how can I simplify this fragment? if arglist: arglist.pop(0) if arglist: self.myparm1 = arglist.pop(0) if arglist: self.myparm2 = arglist.pop(0) if arglist: self.myparm3 = arglist.pop(0) if arglist: self.parm4 = arglist.pop(0) # ... Thanks J^n I often use this convenience function: def getitem(seq, index, default=None): Get item from an `seq` at `index`, return default if index out of range. try : return seq[index] except IndexError : return default If you're ok with setting myparm values to default None, you can do: self.myparm1, self.myparm2, self.myparm3, self.myparm4 = \ (getitem(arglist, n) for n in range(4)) If you only want to set them when they are in arglist: for n in range(4): val = getitem(arglist, n) if val is not None: setattr(self, myparm%d % (n+1), val) -m -- Lark's Tongue Guide to Python: http://lightbird.net/larks/ “So many books, so little time.” ― Frank Zappa -- http://mail.python.org/mailman/listinfo/python-list
Re: suggestions for improving code fragment please
On 02/28/2013 03:37 PM, Tim Chase wrote: On 2013-02-28 19:47, The Night Tripper wrote: Hi there I'm being very dumb ... how can I simplify this fragment? if arglist: arglist.pop(0) if arglist: self.myparm1 = arglist.pop(0) if arglist: self.myparm2 = arglist.pop(0) if arglist: self.myparm3 = arglist.pop(0) if arglist: self.parm4 = arglist.pop(0) If they're arbitrarily named attributes of the self, you could do something like for attr in (myparm1, myparm2, myparm3, ...): if arglist: setattr(self, attr, arglist.pop(0)) else: break -tkc Or something like (untested): for name, value in zip([myparm1, myparm2, myparm3], arglist): setattr(self, name, value) arglist = [] #if you care how it ends up -- DaveA -- http://mail.python.org/mailman/listinfo/python-list
Re: suggestions for improving code fragment please
On 2/28/2013 2:47 PM, The Night Tripper wrote: Hi there I'm being very dumb ... how can I simplify this fragment? if arglist: arglist.pop(0) if arglist: self.myparm1 = arglist.pop(0) if arglist: self.myparm2 = arglist.pop(0) if arglist: self.myparm3 = arglist.pop(0) if arglist: self.parm4 = arglist.pop(0) To literally do the same thing try: arglist.pop(0) self.myparm1 = arglist.pop(0) self.myparm2 = arglist.pop(0) self.myparm3 = arglist.pop(0) self.parm4 = arglist.pop(0) except IndexError: pass However, repeated popping from the front is O(n**2) instead of O(n). Following should do the same, including removal from original arglist. it = iter(arglist) n = 0 try: next(it); n += 1 self.myparm1 = next(it); n += 1 self.myparm2 = next(it); n += 1 self.myparm3 = next(it); n += 1 self.parm4 = next(it); n += 1 except StopIteration: pass arglist = arglist[n:] -- Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: suggestions for improving code fragment please
On 2013-02-28 16:28, Dave Angel wrote: On 02/28/2013 03:37 PM, Tim Chase wrote: for attr in (myparm1, myparm2, myparm3, ...): if arglist: setattr(self, attr, arglist.pop(0)) else: break Or something like (untested): for name, value in zip([myparm1, myparm2, myparm3], arglist): setattr(self, name, value) arglist = [] #if you care how it ends up The OP's code modified arglist by .pop(0) so I maintained the same behavior. This is useful if additional arguments beyond the N named ones are used for some other purpose and you don't want to figure out how many were taken. Otherwise, if one wants to keep arglist, Dave's zip() solution is a cleaner way to go. -tkc -- http://mail.python.org/mailman/listinfo/python-list
Re: suggestions for improving code fragment please
Hi All thanks very much for the various suggestions - very helpful. I think I like one of the 'just catch the exception' approaches, or using Mitya's helper function, which I was clutching towards myself. Either way, lots of food for thought. This forum really is one of the best places around... Cheers Jon N -- http://mail.python.org/mailman/listinfo/python-list
Re: suggestions for improving code fragment please
On Thu, 28 Feb 2013 19:47:12 +, The Night Tripper wrote:
Hi there
I'm being very dumb ... how can I simplify this fragment?
I suggest that the best way to simplify that fragment is to change the
design of your class so it isn't so horrible. As it stands now, your
class defines an arbitrary number of params, which *may or may not exist*:
if arglist:
arglist.pop(0)
if arglist:
self.myparm1 = arglist.pop(0)
if arglist:
self.myparm2 = arglist.pop(0)
if arglist:
self.myparm3 = arglist.pop(0)
if arglist:
self.parm4 = arglist.pop(0)
# ...
So using your class is a horrible experience:
if hasattr(instance, 'param1'):
do_something_with(instance.param1)
else:
fall_back_when_param1_doesnt_exist()
if hasattr(instance, 'param2'):
do_something_with(instance.param2)
else:
fall_back_when_param2_doesnt_exist()
if hasattr(instance, 'param3'):
print Do you hate this class yet?
We have a perfectly good programming idiom to deal with a variable number
of values: the list, or tuple if you prefer. So here's an alternative:
self.params = arglist[1:]
If order is not important:
self.params = set(arglist[1:])
If you have to map names to values:
self.params = dict(
('param%d' % i, value) for i, value in enumerate(arglist[1:])
)
If you absolutely must have named attributes, I recommend that you choose
a default value that indicates missing. Conventionally, that is None,
but you can always create your own sentinel value if needed:
SENTINEL = object()
arglist = arglist + [SENTINEL]*20
for i in range(1, 21):
setattr(self, 'param%d' % i, arglist[i])
--
Steven
--
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