Converting a string to the most probable type

[Pierre Quentel]

Hi,

I would like to know if there is a module that converts a string to a
value of the "most probable type" ; for instance :
- if the string is "abcd" the value is the same string "abcd"
- string "123" : value = the integer 123
- string "-1.23" (or "-1,23" if the locale for decimals is ,) : value
= the float -1.23
- string "2008/03/06" (the format is also locale-dependant) : value =
datetime.date(2 008,03,06)

Like in spreadsheets, special prefixes could be used to force the
type : for instance '123 would be converted to the *string* "123"
instead of the *integer* 123

I could code it myself, but this wheel is probably already invented

Regards,
Pierre

[George Sakkis]

On Mar 6, 9:27 am, Pierre Quentel <quentel.pie... @wanadoo.frwrot e:

Hi,

I would like to know if there is a module that converts a string to a
value of the "most probable type" ; for instance :
- if the string is "abcd" the value is the same string "abcd"
- string "123" : value = the integer 123
- string "-1.23" (or "-1,23" if the locale for decimals is ,) : value
= the float -1.23
- string "2008/03/06" (the format is also locale-dependant) : value =
datetime.date(2 008,03,06)

Like in spreadsheets, special prefixes could be used to force the
type : for instance '123 would be converted to the *string* "123"
instead of the *integer* 123

I could code it myself, but this wheel is probably already invented

Maybe, but that's a so domain-specific and easy to code wheel that
it's no big deal reinventing.

George

[rockingred]

On Mar 6, 3:20*pm, George Sakkis <george.sak...@ gmail.comwrote:

On Mar 6, 9:27 am, Pierre Quentel <quentel.pie... @wanadoo.frwrot e:

Hi,

I would like to know if there is a module that converts a string to a
value of the "most probable type" ; for instance :
- if the string is "abcd" the value is the same string "abcd"
- string "123" : value = the integer 123
- string "-1.23" (or "-1,23" if the locale for decimals is ,) : value
= the float -1.23
- string "2008/03/06" (the format is also locale-dependant) : value =
datetime.date(2 008,03,06)

Like in spreadsheets, special prefixes could be used to force the
type : for instance '123 would be converted to the *string* "123"
instead of the *integer* 123

I could code it myself, but this wheel is probably already invented

Maybe, but that's a so domain-specific and easy to code wheel that
it's no big deal reinventing.

George- Hide quoted text -

- Show quoted text -

Actually you could probably write your own code very easily, a couple
of try/except clauses. I would recommend you try int() first, then
try float(), then try date check and when all else fails leave it a
string. However, it may be an interesting challenge for those who are
willing to make the attempt. "Define Cell/Field contents".

[=?ISO-8859-1?Q?Luis_M=2E_Gonz=E1lez?=]

On 6 mar, 11:27, Pierre Quentel <quentel.pie... @wanadoo.frwrot e:

Hi,

I would like to know if there is a module that converts a string to a
value of the "most probable type" ; for instance :
- if the string is "abcd" the value is the same string "abcd"
- string "123" : value = the integer 123
- string "-1.23" (or "-1,23" if the locale for decimals is ,) : value
= the float -1.23
- string "2008/03/06" (the format is also locale-dependant) : value =
datetime.date(2 008,03,06)

Like in spreadsheets, special prefixes could be used to force the
type : for instance '123 would be converted to the *string* "123"
instead of the *integer* 123

I could code it myself, but this wheel is probably already invented

Regards,
Pierre

>>def convert(x):

if '.' in x:
try: return float(x)
except ValueError: return x
else:
try: return int(x)
except: return x

>>convert('123' )

123

>>convert('123. 99')

123.98999999999 999

>>convert('hell o')

'hello'

[hvendelbo.dev]

On Mar 6, 9:17 pm, Luis M. González <luis...@gmail. comwrote:

On 6 mar, 11:27, Pierre Quentel <quentel.pie... @wanadoo.frwrot e:

Hi,

I would like to know if there is a module that converts a string to a
value of the "most probable type" ; for instance :
- if the string is "abcd" the value is the same string "abcd"
- string "123" : value = the integer 123
- string "-1.23" (or "-1,23" if the locale for decimals is ,) : value
= the float -1.23
- string "2008/03/06" (the format is also locale-dependant) : value =
datetime.date(2 008,03,06)

Like in spreadsheets, special prefixes could be used to force the
type : for instance '123 would be converted to the *string* "123"
instead of the *integer* 123

I could code it myself, but this wheel is probably already invented

Regards,
Pierre

>def convert(x):

if '.' in x:
try: return float(x)
except ValueError: return x
else:
try: return int(x)
except: return x

>convert('123 ')

123

>convert('123.9 9')

123.98999999999 999

>convert('hello ')

'hello'

Neat solution. The real challenge though is whether to support
localised dates, these are all valid:
20/10/01
102001
20-10-2001
20011020

[castironpi]

And so on and so forth. *The tricky bit is how to tell the difference

between Day, Month and Year.

There isn't one.

[Paul Rubin]

Pierre Quentel <qu************ @wanadoo.frwrit es:

I would like to know if there is a module that converts a string to a
value of the "most probable type"

Python 2.4.4 (#1, Oct 23 2006, 13:58:00)

>>import this

The Zen of Python, by Tim Peters
...
In the face of ambiguity, refuse the temptation to guess.

[John Machin]

On Mar 8, 11:13 am, Paul Rubin <http://phr...@NOSPAM.i nvalidwrote:

Pierre Quentel <quentel.pie... @wanadoo.frwrit es:

I would like to know if there is a module that converts a string to a
value of the "most probable type"

Python 2.4.4 (#1, Oct 23 2006, 13:58:00)

>>import this

The Zen of Python, by Tim Peters
...
In the face of ambiguity, refuse the temptation to guess.

Reminds me of the story about the avionics software for a fighter
plane which when faced with the situation of being exactly upside-down
refused to guess whether it should initiate a left roll or a right
roll :-)

[Steven D'Aprano]

On Fri, 07 Mar 2008 16:13:04 -0800, Paul Rubin wrote:

Pierre Quentel <qu************ @wanadoo.frwrit es:

>I would like to know if there is a module that converts a string to a
value of the "most probable type"

Python 2.4.4 (#1, Oct 23 2006, 13:58:00)

>>import this

The Zen of Python, by Tim Peters
...
In the face of ambiguity, refuse the temptation to guess.

Good advice, but one which really only applies to libraries. At the
application level, sometimes (but not always, or even most times!)
guessing is the right thing to do.

E.g. spreadsheet applications don't insist on different syntax for
strings, dates and numbers. You can use syntax to force one or the other,
but by default the application will auto-detect what you want according
to relatively simple, predictable and intuitive rules:

* if the string looks like a date, it's a date;
* if it looks like a number, it's a number;
* otherwise it's a string.

Given the user-base of the application, the consequences of a wrong
guess, and the ease of fixing it, guessing is the right thing to do.

Auto-completion is another good example of guessing in the face of
ambiguity. It's not guessing that is bad, but what you do with the guess.
--
Steven

[Pierre Quentel]

>def convert(x):

>
* * * * if '.' in x:
* * * * * * * * try: return float(x)
* * * * * * * * except ValueError: return x
* * * * else:
* * * * * * * * try: return int(x)
* * * * * * * * except: return x

>convert('123 ')

123

>convert('123.9 9')

123.98999999999 999

>convert('hello ')

Hi,

That's fine for people who write floats with a "." ; but others learn
to enter them with ","

For the same float, the French write the literal 123.456.789,99 when
others write 123,456,789.99 ; for us, today is 8/3/2008 (or
08/03/2008) where for others it's 3/8/2008 or perhaps 2008/3/8

Popular spreadsheets know how to "guess" literals ; if the guess is
not correct users can usually specify the pattern to use. My question
was just to know if something similar had already been developed in
Python ; I understand that the answer is no

Thanks,
Pierre