Re: Creating formatted output using picture strings

python@bdurham.com wrote:

> Does Python provide a way to format a string according to a
> 'picture' format?
>
> For example, if I have a string '123456789' and want it formatted
> like '(123)-45-(678)[9]', is there a module or function that will
> allow me to do this or do I need to code this type of
> transformation myself?

A basic implementation without regular expressions:

>>> def picture(s, pic, placeholder="@"):
.... parts = pic.split(placeholder)
.... result = [None]*(len(parts)+len(s))
.... result[::2] = parts
.... result[1::2] = s
.... return "".join(result)
....
>>>
>>> picture("123456789", "(@@@)-@@-(@@@)[@]")
'(123)-45-(678)[9]'

Peter

2010/2/10 Peter Otten <__peter__@web.de>:
> python@bdurham.com wrote:
>
>> Does Python provide a way to format a string according to a
>> 'picture' format?
>>
>> For example, if I have a string '123456789' and want it formatted
>> like '(123)-45-(678)[9]', is there a module or function that will
>> allow me to do this or do I need to code this type of
>> transformation myself?
>
> A basic implementation without regular expressions:
>
>>>> def picture(s, pic, placeholder="@"):
> ... * * parts = pic.split(placeholder)
> ... * * result = [None]*(len(parts)+len(s))
> ... * * result[::2] = parts
> ... * * result[1::2] = s
> ... * * return "".join(result)
> ...
>>>>
>>>> picture("123456789", "(@@@)-@@-(@@@)[@]")
> '(123)-45-(678)[9]'
>
> Peter
> --
> http://mail.python.org/mailman/listinfo/python-list
>

Inspired by your answer here's another version:

>>> def picture(s, pic):
.... if len(s)==0: return pic
.... if pic[0]=='#': return s[0]+picture(s[1:], pic[1:])
.... return pic[0]+picture(s, pic[1:])
....
>>> picture("123456789", "(###)-##-(###)[#]")
'(123)-45-(678)[9]'
>>>

--
http://olofb.wordpress.com

* Olof Bjarnason:
> 2010/2/10 Peter Otten <__peter__@web.de>:
>> python@bdurham.com wrote:
>>
>>> Does Python provide a way to format a string according to a
>>> 'picture' format?
>>>
>>> For example, if I have a string '123456789' and want it formatted
>>> like '(123)-45-(678)[9]', is there a module or function that will
>>> allow me to do this or do I need to code this type of
>>> transformation myself?
>> A basic implementation without regular expressions:
>>
>>>>> def picture(s, pic, placeholder="@"):
>> ... parts = pic.split(placeholder)
>> ... result = [None]*(len(parts)+len(s))
>> ... result[::2] = parts
>> ... result[1::2] = s
>> ... return "".join(result)
>> ...
>>>>> picture("123456789", "(@@@)-@@-(@@@)[@]")
>> '(123)-45-(678)[9]'
>>
>> Peter
>> --
>> http://mail.python.org/mailman/listinfo/python-list
>>
>
> Inspired by your answer here's another version:
>
>>>> def picture(s, pic):
> ... if len(s)==0: return pic
> ... if pic[0]=='#': return s[0]+picture(s[1:], pic[1:])
> ... return pic[0]+picture(s, pic[1:])
> ...
>>>> picture("123456789", "(###)-##-(###)[#]")
> '(123)-45-(678)[9]'

I learned a bit by Peter Otten's example; I would have gotten to that notation
sooner or later, but that example made it 'sooner' :-).

I think your version is cute.

I'd probably write it in a non-recursive way, though, like

def picture( s, pic, placeholder = "@" ):
result = ""
char_iter = iter( s )
for c in pic:
result += c if c != placeholder else next( char_iter )
return result

Of course this is mostly personal preference, but there is also a functional
difference.

With your version an IndexError will be raised if there are too /many/
characters in s, while too few characters in s will yield "#" in the result.

With my version a StopIteration will be raised if there are to /few/ characters
in s, while too many characters will just have the extraneous chars ignored.


Cheers,

- Alf

2010/2/10 Alf P. Steinbach <alfps@start.no>:
> * Olof Bjarnason:
>>
>> 2010/2/10 Peter Otten <__peter__@web.de>:
>>>
>>> python@bdurham.com wrote:
>>>
>>>> Does Python provide a way to format a string according to a
>>>> 'picture' format?
>>>>
>>>> For example, if I have a string '123456789' and want it formatted
>>>> like '(123)-45-(678)[9]', is there a module or function that will
>>>> allow me to do this or do I need to code this type of
>>>> transformation myself?
>>>
>>> A basic implementation without regular expressions:
>>>
>>>>>> def picture(s, pic, placeholder="@"):
>>>
>>> ... * * parts = pic.split(placeholder)
>>> ... * * result = [None]*(len(parts)+len(s))
>>> ... * * result[::2] = parts
>>> ... * * result[1::2] = s
>>> ... * * return "".join(result)
>>> ...
>>>>>>
>>>>>> picture("123456789", "(@@@)-@@-(@@@)[@]")
>>>
>>> '(123)-45-(678)[9]'
>>>
>>> Peter
>>> --
>>> http://mail.python.org/mailman/listinfo/python-list
>>>
>>
>> Inspired by your answer here's another version:
>>
>>>>> def picture(s, pic):
>>
>> ... * if len(s)==0: return pic
>> ... * if pic[0]=='#': return s[0]+picture(s[1:], pic[1:])
>> ... * return pic[0]+picture(s, pic[1:])
>> ...
>>>>>
>>>>> picture("123456789", "(###)-##-(###)[#]")
>>
>> '(123)-45-(678)[9]'
>
> I learned a bit by Peter Otten's example; I would have gotten to that
> notation sooner or later, but that example made it 'sooner' :-).
>
> I think your version is cute.

Thanks!

Here's another version (maybe a little more readable?):

def first(s): return s[0]

def rest(s): return s[1:]

def picture(s, pic):
if not s: return pic
if first(pic)=='#': return first(s)+picture(rest(s), rest(pic))
return first(pic)+picture(s, rest(pic))


>
> I'd probably write it in a non-recursive way, though, like
>
> * *def picture( s, pic, placeholder = "@" ):
> * * * *result = ""
> * * * *char_iter = iter( s )
> * * * *for c in pic:
> * * * * * *result += c if c != placeholder else next( char_iter )
> * * * *return result
>
> Of course this is mostly personal preference, but there is also a functional
> difference.
>
> With your version an IndexError will be raised if there are too /many/
> characters in s, while too few characters in s will yield "#" in the result.
>
> With my version a StopIteration will be raised if there are to /few/
> characters in s, while too many characters will just have the extraneous
> chars ignored.
>
>
> Cheers,
>
> - Alf
> --
> http://mail.python.org/mailman/listinfo/python-list
>



--
http://olofb.wordpress.com

Olof Bjarnason wrote:
> 2010/2/10 Peter Otten <__peter__@web.de>:
>> python@bdurham.com wrote:
>>
>>> Does Python provide a way to format a string according to a
>>> 'picture' format?
>>>
>>> For example, if I have a string '123456789' and want it formatted
>>> like '(123)-45-(678)[9]', is there a module or function that will
>>> allow me to do this or do I need to code this type of
>>> transformation myself?
>> A basic implementation without regular expressions:
>>
>>>>> def picture(s, pic, placeholder="@"):
>> ... parts = pic.split(placeholder)
>> ... result = [None]*(len(parts)+len(s))
>> ... result[::2] = parts
>> ... result[1::2] = s
>> ... return "".join(result)
>> ...
>>>>> picture("123456789", "(@@@)-@@-(@@@)[@]")
>> '(123)-45-(678)[9]'
>>
>> Peter
>> --
>> http://mail.python.org/mailman/listinfo/python-list
>>
>
> Inspired by your answer here's another version:
>
>>>> def picture(s, pic):
> ... if len(s)==0: return pic
> ... if pic[0]=='#': return s[0]+picture(s[1:], pic[1:])
> ... return pic[0]+picture(s, pic[1:])
> ...
>>>> picture("123456789", "(###)-##-(###)[#]")
> '(123)-45-(678)[9]'
>
Here's a version without recursion:

>>> def picture(s, pic):
.... pic = pic.replace("%", "%%").replace("#", "%s")
.... return pic % tuple(s)
....
>>> picture("123456789", "(###)-##-(###)[#]")
'(123)-45-(678)[9]'

Hi Tim,

Thank you very much for your update to MRAB's creative solution.

> You don't give the expected output for these test cases, so
> it's hard to tell whether you want to pad-left or pad-right.

To be honest, I wasn't sure myself

My original post was the result of doing some simple formatting where my
input strings were 'guaranteed'<g> to be a consistent length. I hadn't
started to think about the specs for a more universal picture function
until I started to study and test the solutions proposed by others. It
bears repeating again - what a clever mix of techniques - I really
learned a lot more than I was expecting!

I appreciate you taking the extra time to analyze the problem and refine
it further.

Cheers,
Malcolm

Riffing on MRAB's lovely solution, you can do something like

def picture(
s, pic,
placeholder='@',
padding=' ',
pad_left=True
):
assert placeholder != '%'
s = str(s)
expected = pic.count(placeholder)
if len(s) > expected:
s = s[:expected]
if len(s) < expected:
if pad_left:
s = s.rjust(expected, padding)
else:
s = s.ljust(expected, padding)
return pic.replace(
'%', '%%').replace(
placeholder, '%s') % tuple(s)

print picture("123456789", "(@@@)-@@-(@@@)[@]", pad_left=False)
print picture("123456789ABC", "(@@@)-@@-(@@@)[@]", pad_left=False)
print picture("1234", "(@@@)-@@-(@@@)[@]", pad_left=False)
print picture("123456789", "(@@@)-@@-(@@@)", pad_left=False)
print picture("123456789", "(@@@)-@@-(@@@)[@][@@@@@]",
pad_left=False)

That way you can specify your placeholder, your padding
character, and whether you want it to pad to the left or right.

On 10/02/2010 20:36, python@bdurham.com wrote:
> def picture(s, pic, placeholder='@'):
> nextchar=iter(s).next
> return ''.join(nextchar() if i == placeholder else i for i in pic)
Hell's teeth - even I understood that! Amazing solution.

\d

--
Fonty Python and Things! -- http://otherwise.relics.co.za/wiki/Software

On 2010-02-10, python@bdurham.com <python@bdurham.com> wrote:

[regardning "picture" output format specifiers]

> I was thinking that there was a built-in function for this
> common(?) use case

I haven't seen that paradigm since my one-and-only exposure to
COBOL in a class I took back in 1979. Is the "picture" thing
commonly used in other places than COBOL?

--
Grant Edwards grante Yow! Did I say I was
at a sardine? Or a bus???
visi.com

On Feb 10, 2010, at 2:57 PM, Grant Edwards wrote:

> On 2010-02-10, python@bdurham.com <python@bdurham.com> wrote:
>
> [regardning "picture" output format specifiers]
>
>> I was thinking that there was a built-in function for this
>> common(?) use case
>
> I haven't seen that paradigm since my one-and-only exposure to
> COBOL in a class I took back in 1979. Is the "picture" thing
> commonly used in other places than COBOL?

Seriously?

I've seen it in dozens places other than COBOL over the years in everything from templating languages to report generators, to built-in support in a variety of languages (dBASE II anyone?).

Haven't you ever had to get a e.g. a phone number or social security number from user input?

S

Grant Edwards wrote:
> [regardning "picture" output format specifiers]
>> I was thinking that there was a built-in function for this
>> common(?) use case
>
> I haven't seen that paradigm since my one-and-only exposure to
> COBOL in a class I took back in 1979. Is the "picture" thing
> commonly used in other places than COBOL?

I've spotted in the wild as recently as Visual Basic 6. I don't
know if remnants made it into Visual Fred (VB.net). I think
they're referred to as "format strings", but they're a mystical
(and poorly documented) suite of characters that seem to have
accrued features like my bathtub gets mildew. Most folks just
copy and paste the format strings from the web.

-tkc

On 2010-02-10, ssteinerX@gmail.com <ssteinerx@gmail.com> wrote:
> On Feb 10, 2010, at 2:57 PM, Grant Edwards wrote:
>
>> On 2010-02-10, python@bdurham.com <python@bdurham.com> wrote:
>>
>> [regardning "picture" output format specifiers]
>>
>>> I was thinking that there was a built-in function for this
>>> common(?) use case
>>
>> I haven't seen that paradigm since my one-and-only exposure to
>> COBOL in a class I took back in 1979. Is the "picture" thing
>> commonly used in other places than COBOL?
>
> Seriously?

Seriously.

> I've seen it in dozens places other than COBOL over the years
> in everything from templating languages to report generators,
> to built-in support in a variety of languages (dBASE II
> anyone?).
>
> Haven't you ever had to get a e.g. a phone number or social
> security number from user input?

Nope. I guess it's specific to certain application areas. I've
never done any database type stuff. I do mostly embedded,
device drivers, networking/protocols, industrial automation,
Unix system admin/automation, and scientific visualization.

--
Grant Edwards grante Yow! I once decorated my
at apartment entirely in ten
visi.com foot salad forks!!

On Feb 10, 2010, at 3:40 PM, Grant Edwards wrote:

> On 2010-02-10, ssteinerX@gmail.com <ssteinerx@gmail.com> wrote:
>> On Feb 10, 2010, at 2:57 PM, Grant Edwards wrote:
>>
>>> On 2010-02-10, python@bdurham.com <python@bdurham.com> wrote:
>>>
>>> [regardning "picture" output format specifiers]
>>>
>>>> I was thinking that there was a built-in function for this
>>>> common(?) use case
>>>
>>> I haven't seen that paradigm since my one-and-only exposure to
>>> COBOL in a class I took back in 1979. Is the "picture" thing
>>> commonly used in other places than COBOL?
>>
>> Seriously?
>
> Seriously.
>
>> I've seen it in dozens places other than COBOL over the years
>> in everything from templating languages to report generators,
>> to built-in support in a variety of languages (dBASE II
>> anyone?).
>>
>> Haven't you ever had to get a e.g. a phone number or social
>> security number from user input?
>
> Nope. I guess it's specific to certain application areas. I've
> never done any database type stuff. I do mostly embedded,
> device drivers, networking/protocols, industrial automation,
> Unix system admin/automation, and scientific visualization.

Yah, I've hardly ever had to get SSN input from users in a device driver ;-).

That's what makes groups like this go 'round; we have all done different types of things which gives us all different perspectives.

S

On 2/10/2010 2:57 PM, Grant Edwards wrote:
> On 2010-02-10, python@bdurham.com<python@bdurham.com> wrote:
>
> [regardning "picture" output format specifiers]
>
>> I was thinking that there was a built-in function for this
>> common(?) use case
>
> I haven't seen that paradigm since my one-and-only exposure to
> COBOL in a class I took back in 1979. Is the "picture" thing
> commonly used in other places than COBOL?
>

FWIW, Microsoft Excel supports "Custom" numeric cell formats that use a
PICTURE-like syntax.

-John