alternating string replace

[cesco]

Hi,

say I have a string like the following:
s1 = 'hi_cat_bye_dog '
and I want to replace the even '_' with ':' and the odd '_' with ','
so that I get a new string like the following:
s2 = 'hi:cat,bye:dog '
Is there a common recipe to accomplish that? I can't come up with any
solution...

Thanks in advance
Cesco

[cokofreedom]

On Jan 9, 11:34 am, cesco <fd.calabr...@g mail.comwrote:

Hi,

say I have a string like the following:
s1 = 'hi_cat_bye_dog '
and I want to replace the even '_' with ':' and the odd '_' with ','
so that I get a new string like the following:
s2 = 'hi:cat,bye:dog '
Is there a common recipe to accomplish that? I can't come up with any
solution...

Thanks in advance
Cesco

For replacing every other one, I tend to use the modulo, with a
counter.

count = (if u want even start with 0 else do 1)

while/for replacing /in lalastring:
if count % 2 == 0:
do even
else:
do odd
count += 1

This is a rather basic way of doing it, and I am sure people will sure
much more efficient ways, but it generally works for me.

Though I am now wondering if count % 2 when count == 2 is true or
false as it returns 0

Of course you still need to do your replace but you should be able to
do that.

[Fredrik Lundh]

cesco wrote:

and I want to replace the even '_' with ':' and the odd '_' with ','
so that I get a new string like the following:
s2 = 'hi:cat,bye:dog '
Is there a common recipe to accomplish that? I can't come up with any
solution...

how about splitting on "_", joining pairs with ":", and finally joining
the result with "," ?

>>s1 = "hi_cat_bye_dog "
s1 = s1.split("_")
s1

['hi', 'cat', 'bye', 'dog']

>>s1 = [s1[i]+":"+s1[i+1] for i in range(0,len(s1) ,2)]
s1

['hi:cat', 'bye:dog']

>>s1 = ",".join(s1 )
s1

'hi:cat,bye:dog '

(there are many other ways to do it, but the above 3-liner is short and
straightforward . note the use of range() to step over every other item
in the list)

</F>

[Peter Otten]

cesco wrote:

say I have a string like the following: s1 = 'hi_cat_bye_dog '
and I want to replace the even '_' with ':' and the odd '_' with ',' so
that I get a new string like the following: s2 = 'hi:cat,bye:dog '

>>import re
from itertools import cycle
re.sub("_", lambda m, c=cycle(":,").n ext: c(), "hi_cat_bye_dog ")

'hi:cat,bye:dog '

Is there a common recipe to accomplish that? I can't come up with any
solution...

There are many. If you want to learn Python don't be afraid to write it
in a long-winded way (with loops and helper functions) first.

Peter

[Duncan Booth]

cesco <fd**********@g mail.comwrote:

Hi,

say I have a string like the following:
s1 = 'hi_cat_bye_dog '
and I want to replace the even '_' with ':' and the odd '_' with ','
so that I get a new string like the following:
s2 = 'hi:cat,bye:dog '
Is there a common recipe to accomplish that? I can't come up with any
solution...

Here's yet another answer:

from itertools import islice, cycle

def interleave(*ite rators):
iterators = [ iter(i) for i in iterators ]
while 1:
for i in iterators:
yield i.next()
def punctuate(s):
parts = s.split('_')
punctuation = islice(cycle(': ,'), len(parts)-1)
return ''.join(interle ave(parts, punctuation))

s1 = 'hi_cat_bye_dog '
print punctuate(s1)
# Or as a one-liner (once you have interleave):

print ''.join(list(in terleave(s1.spl it('_'), cycle(':,')))[:-1])

[bearophileHUGS]

My version, uses a re.sub, plus a function used as an object with a
one bit state:

from re import sub

def repl(o):
repl.n = not repl.n
return ":" if repl.n else ","
repl.n = False

print sub("_", repl, "hi_cat_bye_dog _foo_bar_red")

Bye,
bearophile

[cokofreedom]

Designed a pretty basic way that is "acceptable " on small strings.

evenOrOdd = True
s1 = "hi_cat_bye_dog _foo_bar_red"
s2 = ""

for i in s1:
if i == '_':
if evenOrOdd:
s2 += ':'
evenOrOdd = not evenOrOdd
else:
s2 += ','
evenOrOdd = not evenOrOdd
else:
s2 += i

print s2

[Neil Cerutti]

On Jan 9, 2008 5:34 AM, cesco <fd**********@g mail.comwrote:

Hi,

say I have a string like the following:
s1 = 'hi_cat_bye_dog '
and I want to replace the even '_' with ':' and the odd '_' with ','
so that I get a new string like the following:
s2 = 'hi:cat,bye:dog '
Is there a common recipe to accomplish that? I can't come up with any
solution...

Thanks in advance

Hum, hum... If I had a hammer...

from pyparsing import *

word = Word(alphas)
sep = Literal('_').su ppress()
pair = Group(word + sep + word)
pairs = delimitedList(p air, '_')

print ','.join(':'.jo in(t) for t in
pairs.parseStri ng('hi_cat_bye_ dog').asList())

--
Neil Cerutti <mr************ ***@gmail.com>

[Neil Cerutti]

On Jan 9, 2008 5:34 AM, cesco <fd**********@g mail.comwrote:

Hi,

say I have a string like the following:
s1 = 'hi_cat_bye_dog '
and I want to replace the even '_' with ':' and the odd '_' with ','
so that I get a new string like the following:
s2 = 'hi:cat,bye:dog '
Is there a common recipe to accomplish that? I can't come up with any
solution...

Thanks in advance

Hum, hum... If I had a hammer...
from pyparsing import *

word = Word(alphas)
sep = Literal('_').su ppress()
pair = Group(word + sep + word)
pairs = delimitedList(p air, '_')

print ','.join(':'.jo in(t) for t in
pairs.parseStri ng('hi_cat_bye_ dog').asList())

--
Neil Cerutti <mr************ ***@gmail.com>

[Pablo Ziliani]

cesco wrote:

Hi,

say I have a string like the following:
s1 = 'hi_cat_bye_dog '
and I want to replace the even '_' with ':' and the odd '_' with ','
so that I get a new string like the following:
s2 = 'hi:cat,bye:dog '
Is there a common recipe to accomplish that? I can't come up with any
solution...

What about:

>>import re
s1 = 'hi_cat_bye_dog '
print re.sub(r'([^_]+)_([^_]+)_?', r'\1:\2;', s1)

hi:cat;bye:dog;

it still works for a longer string:

>>s1 = 'hi_cat_bye_dog _' + s1
s1

'hi_cat_bye_dog _hi_cat_bye_dog '

>>print re.sub(r'([^_]+)_([^_]+)_?', r'\1:\2;', s1)

hi:cat;bye:dog; hi:cat;bye:dog;