I'm starting to think like a Pythonista

[brad]

I was looking at a way to implement Ruby's upto method in python. I came
up with the code below... three years ago, I would never have thought of
list comprehension, today it seems second nature. This may be totally
un-Pythonic, but I thought it was kind of clever. Man, for some reason,
I feel like being rude and lofty acting

low_odds = [1,3,5,7,9]
# make a list containing 10 - 98 evens only
big_evens = big_evens = [x for x in list(xrange(99)) if x % 2 == 0 and
x >8]

low_evens = [2,4,6,8]
# make a list containing 11 - 99 odds only
big_odds = [x for x in list(xrange(100)) if x % 2 != 0 and x >9]

y = 8

if y in low_evens:
ok_numbers = low_odds + big_evens + [x for x in low_evens if x <= y]

 

[Erik Jones]

I was looking at a way to implement Ruby's upto method in python. I
came
up with the code below... three years ago, I would never have
thought of
list comprehension, today it seems second nature. This may be totally
un-Pythonic, but I thought it was kind of clever. Man, for some
reason,
I feel like being rude and lofty acting

low_odds = [1,3,5,7,9]
# make a list containing 10 - 98 evens only
big_evens = big_evens = [x for x in list(xrange(99)) if x % 2 == 0
and
x >8]

big_evens = range(10, 100, 2)

low_evens = [2,4,6,8]
# make a list containing 11 - 99 odds only
big_odds = [x for x in list(xrange(100)) if x % 2 != 0 and x >9]

big_odds = range(11, 100, 2)


Erik Jones

Software Developer | Emma®
(e-mail address removed)
800.595.4401 or 615.292.5888
615.292.0777 (fax)

Emma helps organizations everywhere communicate & market in style.
Visit us online at http://www.myemma.com

 

[Bjoern Schliessmann]

low_odds = [1,3,5,7,9]
# make a list containing 10 - 98 evens only
big_evens = big_evens = [x for x in list(xrange(99)) if x % 2 ==
0 and x >8]

Why use xrange if you convert it to a full list in place? No
advantage there.

Regards,


Björn

 

[brad]

low_odds = [1,3,5,7,9]
# make a list containing 10 - 98 evens only
big_evens = big_evens = [x for x in list(xrange(99)) if x % 2 ==
0 and x >8]

Why use xrange if you convert it to a full list in place? No
advantage there.

What is the dis-advantage of using xrange over range in this circumstance?

 

[brad]

big_evens = range(10, 100, 2)
big_odds = range(11, 100, 2)

Neat, but not as clever or as hard to read as mine... I'll bet it faster
though... maybe not.

The upto part is here:

ok_numbers = low_odds + big_evens + [x for x in low_evens if x <= y]

 

[Marc 'BlackJack' Rintsch]

low_odds = [1,3,5,7,9]
# make a list containing 10 - 98 evens only
big_evens = big_evens = [x for x in list(xrange(99)) if x % 2 ==
0 and x >8]

Why use xrange if you convert it to a full list in place? No
advantage there.

What is the dis-advantage of using xrange over range in this circumstance?

It's an unnecessary intermediate step.

Ciao,
Marc 'BlackJack' Rintsch

 

[Erik Jones]

brad wrote:
low_odds = [1,3,5,7,9]
# make a list containing 10 - 98 evens only
big_evens = big_evens = [x for x in list(xrange(99)) if x % 2 ==
0 and x >8]

Why use xrange if you convert it to a full list in place? No
advantage there.

What is the dis-advantage of using xrange over range in this
circumstance?

It's an unnecessary intermediate step.

Exactly, there's no disadvantage, but the use case for xrange is for
when there is an advantage. xrange is a lazy generator, which means
that the values in the range are generated one by one, i.e. the
entire range is never present in memory all at once. If all your
doing is building that list then there's no advantage. In fact, [x
for x in xrange(99)] can be though of as longhand for range(99). Put
another way, xrange returns a generator of successive, individual
numbers over a range (optionally with a step) while range returns a
list of numbers over a range (optionally with a step).
<type 'list'>


Erik Jones

Software Developer | Emma®
(e-mail address removed)
800.595.4401 or 615.292.5888
615.292.0777 (fax)

Emma helps organizations everywhere communicate & market in style.
Visit us online at http://www.myemma.com

 

[Bjoern Schliessmann]

Bjoern Schliessmann wrote:

What is the dis-advantage of using xrange over range in this
circumstance?

Hardly any, but honestly: Converting it to a list manually is more
than superfluous.

Regards,


Björn