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Re: formatting list -> comma separated (slightly different)

Paul & Robert wrote...
d = ["soep", "reeds", "ook"]
print ', '.join(d)
soep, reeds, ook
I occasionally have a need for printing lists of items too, but in the form:
"Butter, Cheese, Nuts and Bolts". The last separator is the word 'and'
instead of the comma. The clearest I could come up with in Python is below.
I wonder if there is a more pythonic solution for this problem. Maybe
something recursive?

Greetings,
'''
Formatting a sequence of items such that they are separated by
commas, except the last item, which is separated by the word 'and'.

Used for making lists of dates and items more human-readable
in generated emails and webpages.

For example:

Four friends have a dinner: Anne, Bob, Chris and Debbie
Three friends have a dinner: Anne, Bob and Chris
Two friends have a dinner: Anne and Bob
One friend has a dinner: Anne
No friend has a dinner:

['Anne','Bob','Chris','Debbie'] -"Anne, Bob, Chris and Debbie"
['Bob','Chris','Debbie'] -"Bob, Chris and Debbie"
['Chris','Debbie'] -"Chris and Debbie"
['Debbie'] -"Debbie"
[] -""

'''

def pretty(f):
if len(f)==0: return ''
if len(f)==1: return f[0]
sepwithcommas=f[:-1]
sepwithand=f[-1]
s=', '.join(sepwithcommas)
if sepwithand:
s+=' and '+sepwithand
return s

friends=['Anne','Bob','Chris','Debbie','Eve','Fred']
while True:
print friends,'->',pretty(friends)
if friends:
friends.pop(0)
else:
break

--
"The ability of the OSS process to collect and harness
the collective IQ of thousands of individuals across
the Internet is simply amazing." - Vinod Vallopillil
http://www.catb.org/~esr/halloween/halloween4.html

Jul 9 '08 #1
3 1427
Michiel Overtoom wrote:
Paul & Robert wrote...
>d = ["soep", "reeds", "ook"]
print ', '.join(d)
soep, reeds, ook

I occasionally have a need for printing lists of items too, but in the form:
"Butter, Cheese, Nuts and Bolts". The last separator is the word 'and'
instead of the comma. The clearest I could come up with in Python is below.
I wonder if there is a more pythonic solution for this problem. Maybe
something recursive?

Greetings,
'''
Formatting a sequence of items such that they are separated by
commas, except the last item, which is separated by the word 'and'.

Used for making lists of dates and items more human-readable
in generated emails and webpages.

For example:

Four friends have a dinner: Anne, Bob, Chris and Debbie
Three friends have a dinner: Anne, Bob and Chris
Two friends have a dinner: Anne and Bob
One friend has a dinner: Anne
No friend has a dinner:

['Anne','Bob','Chris','Debbie'] -"Anne, Bob, Chris and Debbie"
['Bob','Chris','Debbie'] -"Bob, Chris and Debbie"
['Chris','Debbie'] -"Chris and Debbie"
['Debbie'] -"Debbie"
[] -""

'''

def pretty(f):
if len(f)==0: return ''
if len(f)==1: return f[0]
sepwithcommas=f[:-1]
sepwithand=f[-1]
s=', '.join(sepwithcommas)
if sepwithand:
s+=' and '+sepwithand
return s

friends=['Anne','Bob','Chris','Debbie','Eve','Fred']
while True:
print friends,'->',pretty(friends)
if friends:
friends.pop(0)
else:
break


IMHO slightly easier to read and faster if the lists are long:

def pretty(f):
if len(f) == 0 :
return ""
elif len(f) == 1:
return f[0]
else:
return ', '.join(f[:-1]) + ' and ' + f[-1]
-Larry
Jul 9 '08 #2
Michiel Overtoom <mo****@xs4all.nlwrote:
I occasionally have a need for printing lists of items too, but in the
form: "Butter, Cheese, Nuts and Bolts". The last separator is the
word 'and' instead of the comma. The clearest I could come up with in
Python is below. I wonder if there is a more pythonic solution for
this problem. Maybe something recursive?
>>from itertools import chain, repeat
def across(*iterables):
iterables = map(iter, iterables)
while 1:
for it in iterables:
yield it.next()

>>friends=['Anne','Bob','Chris','Debbie','Eve','Fred']
''.join(across(friends, chain(repeat(', ', len(friends)-2), [' and
'])))
'Anne, Bob, Chris, Debbie, Eve and Fred'

I feel there ought to be an easier way of alternating between iterators but
if there is I can't think of it offhand. Also it breaks down unless you
have at least two friends.

This version is a bit messy but seems to work reliably for any number of
friends:
>>for i in range(len(friends)+1):
f = friends[:i]
print ' and '.join(s for s in [', '.join(f[:-1]), ''.join(f[-1:])] if
s)

Anne
Anne and Bob
Anne, Bob and Chris
Anne, Bob, Chris and Debbie
Anne, Bob, Chris, Debbie and Eve
Anne, Bob, Chris, Debbie, Eve and Fred

Of course neither works cleanly if you give it an iterator rather than a
list. This is a bit longer but does work without knowing the length of the
iterator in advance (and you could save a couple of lines by concatenating
the adjacent yields):
>>def commaand(it):
it = iter(it)
yield it.next()
n = it.next()
for nxt in it:
yield ', '
yield n
n = nxt
yield ' and '
yield n

>>for i in range(len(friends)+1):
f = friends[:i]
print ''.join(commaand(f))

Anne
Anne and Bob
Anne, Bob and Chris
Anne, Bob, Chris and Debbie
Anne, Bob, Chris, Debbie and Eve
Anne, Bob, Chris, Debbie, Eve and Fred
Jul 9 '08 #3
On 9 Juli, 22:25, Michiel Overtoom <mot...@xs4all.nlwrote:
Paul & Robert wrote...
d = ["soep", "reeds", "ook"]
print ', '.join(d)
soep, reeds, ook

I occasionally have a need for printing lists of items too, but in the form:
"Butter, Cheese, Nuts and Bolts". *The last separator is the word 'and'
instead of the comma. The clearest I could come up with in Python is below.
I wonder if there is a more pythonic solution for this problem. *Maybe
something recursive?
[snip]
def pretty(f):
* * if len(f)==0: return ''
* * if len(f)==1: return f[0]
* * sepwithcommas=f[:-1]
* * sepwithand=f[-1]
* * s=', '.join(sepwithcommas)
* * if sepwithand:
* * * * s+=' and '+sepwithand
* * return s
def pretty(names):
return ' and '.join(', '.join(names).rsplit(', ', 1))

friends=['Anne','Bob','Chris','Debbie','Eve','Fred']
print pretty(friends)
Jul 22 '08 #4

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