text manipulation

[Johhny]

Hello,

I am trying to write a script in python (to replace a perl script with
limited functionality). Now I have some issues. Currently I am using
the perl to load the file then regex parse certain lines to remove
characters (uncomment lines and change variables). I would like to take
that into the python script. I have had a look at the module "string"
and I dont think its what Im looking for.

Here is an example of some text I would like to manipulate

#comment here
#user_defined_v ariable = no
#

I would like to make that

#comment here
user_defined_va riable = yes
#

With perl/sed Its very easy, However Im having issues to do it in
python. Any advice would be great.

Regards,

Johhny.

[Isaac T Alston]

Re: text manipulation

Johhny wrote:
[color=blue]
> Any advice would be great.[/color]


Have you had a look at Python's re module? If you've not, I suggest you do
so - it contains all of Python's regex tools which you'll need.

Regards,

--
Isaac

[Martin Franklin]

Re: text manipulation

Johhny wrote:[color=blue]
> Hello,
>
> I am trying to write a script in python (to replace a perl script with
> limited functionality). Now I have some issues. Currently I am using
> the perl to load the file then regex parse certain lines to remove
> characters (uncomment lines and change variables). I would like to take
> that into the python script. I have had a look at the module "string"
> and I dont think its what Im looking for.
>
> Here is an example of some text I would like to manipulate
>
> #comment here
> #user_defined_v ariable = no
> #
>
> I would like to make that
>
> #comment here
> user_defined_va riable = yes
> #
>
> With perl/sed Its very easy, However Im having issues to do it in
> python. Any advice would be great.
>
> Regards,
>
> Johhny.
>[/color]


forget regular expressions for this job... strings have methods in
python so for example:


for line in file:
if line.startswith ("#user_defined _variable = no"):
line.replace("# user_defined_va riable = no",
"user_defined_v ariable = yes")

.... continue processing file / writing out stuff as you go


Cheers
Martin

[Juho Schultz]

Re: text manipulation

Johhny wrote:[color=blue]
> Hello,
>
> I am trying to write a script in python (to replace a perl script with
> limited functionality). Now I have some issues. Currently I am using
> the perl to load the file then regex parse certain lines to remove
> characters (uncomment lines and change variables). I would like to take
> that into the python script. I have had a look at the module "string"
> and I dont think its what Im looking for.
>
> Here is an example of some text I would like to manipulate
>
> #comment here
> #user_defined_v ariable = no
> #
>
> I would like to make that
>
> #comment here
> user_defined_va riable = yes
> #
>
> With perl/sed Its very easy, However Im having issues to do it in
> python. Any advice would be great.
>
> Regards,
>
> Johhny.
>[/color]

Have you also looked at the built-in string methods?


The following script is probably something you
could start with - it just uncomments lines
and replaces values of some variables.

# dictionary of the variable names
# contains the replacement values
newvalues = {'userdefinedva r1':'yes',
'userdefinedvar 2':'123.654.345 .234'}

# read file to input
output = []
for line in input:
# check if it is a comment with "="
if line.startswith ('#') and ('=' in line):
name, oldvalue = (line.lstrip('# ')).split('=')
# line.lstrip removes leading comments,
# split('=') finds the assignment
if newvalues.has_k ey(name):
# replace line
output.append(" %s = %s" % (name, newvalue[name]))
else:
# or just uncomment
output.append(" %s = %s" % (name, oldvalue))
else:
output.append(l ine)

# write output to file

[Martin Franklin]

Re: text manipulation

Martin Franklin wrote:[color=blue]
> Johhny wrote:
>[color=green]
>>Hello,
>>
>>I am trying to write a script in python (to replace a perl script with
>>limited functionality). Now I have some issues. Currently I am using
>>the perl to load the file then regex parse certain lines to remove
>>characters (uncomment lines and change variables). I would like to take
>>that into the python script. I have had a look at the module "string"
>>and I dont think its what Im looking for.
>>
>>Here is an example of some text I would like to manipulate
>>
>>#comment here
>>#user_defined _variable = no
>>#
>>
>>I would like to make that
>>
>>#comment here
>>user_defined_ variable = yes
>>#
>>
>>With perl/sed Its very easy, However Im having issues to do it in
>>python. Any advice would be great.
>>
>>Regards,
>>
>>Johhny.
>>[/color]
>
>
>
> forget regular expressions for this job... strings have methods in
> python so for example:
>
>
> for line in file:
> if line.startswith ("#user_defined _variable = no"):
> line.replace("# user_defined_va riable = no",
> "user_defined_v ariable = yes")
>
> ... continue processing file / writing out stuff as you go
>
>
> Cheers
> Martin
>[/color]




whoops forgot string methods return the new string.....

for line in file:
if line.startswith ("#user_defined _variable = no"):
line = line.replace("# user_defined_va riable = no",
"user_defined_v ariable = yes")

[BartlebyScrivener]

Re: text manipulation

John,

Martin is right. Always try to solve without regex first. However, for
those situations where you definitely need regex, use this tutorial:

http://www.amk.ca/python/howto/regex/

It's well-written, succinct, and Python-specific.

rpd