Inserting '-' character in front of all numbers in a string

[Michael Bentley]

On Mar 30, 2007, at 4:41 PM, Paul McGuire wrote:

> On Mar 30, 2:09 pm, Michael Bentley <mich... at jedimindworks.com> wrote:
>> On Mar 30, 2007, at 10:38 AM, kevinliu23 wrote:
>>
>>
>>
>>
>>
>>> I want to be able to insert a '-' character in front of all numeric
>>> values in a string. I want to insert the '-' character to use in
>>> conjunction with the getopt.getopt() function.
>>
>>> Rigt now, I'm implementing a menu system where users will be able to
>>> select a set of options like "2a 3ab" which corresponds to menu
>>> choices. However, with getopt.getopt(), it'll only return what I  
>>> want
>>> if I input -2a -3ab as my string. I don't want the user have to  
>>> insert
>>> a '-' character in front of all their choices, so I was thinking of
>>> accepting the string input first, then adding in the '-' character
>>> myself.
>>
>>> So my qusetion is, how do I change:
>>
>>> "2a 3ab" into "-2a -3ab".
>>
>> Will the first character always be a digit?
>>
>> for i in yourstring.split():
>>         if i[0].isdigit():
>>                 yourstring = yourstring.replace(i, '-%s' % (i,))
>>
>> Or are these hex numbers?- Hide quoted text -
>>
>> - Show quoted text -
>
> Your replace strategy is risky.  If:
>
> yourstring = "1ab 2bc 3de 11ab"
>
> it will convert to
>
> -1ab -2bc -3de 1-1ab

True enough!  Good catch!  How's this?

for i in yourstring.split():
	if i[0].isdigit():
		yourstring = yourstring.replace(i, '-%s' % (i,), 1)