How to dynamically assign variables

Dev Shed Forums Sponsor:

May 15th, 2004, 11:34 AM

tdw

Registered User

Join Date: May 2004

Location: London UK

Posts: 4

Time spent in forums: < 1 sec
Reputation Power: 0

How to dynamically assign variables

[Python Newbie]

I want to iterate through a file to read lines of pairs of values and dynamically create and set variables.

eg

line = Variable1 Value1

to create Variable1 with a value of Value1

I don't know what the pairs will contain before reading the file.

ConfigParser looks like it will do the job, but I can't figure out how (I don't want the variable to be in a Dict). Using open() and stepping through the lines allows me to grab the 2 items, but I can't work out how to assign a variable based on the 2 items.

Any help appreciated

May 15th, 2004, 12:13 PM

xlordt

Only the strong survives!!.

Dev Shed God 1st Plane (5500 - 5999 posts)

Join Date: Feb 2003

Location: A World of wonders.

Posts: 5,573

Folding Points: 111202 Folding Title: Super Ultimate Folder - Level 1

Time spent in forums: 1 Month 11 h 9 m 33 sec
Reputation Power: 406

Send a message via Google Talk to xlordt

Can you show me an example of what you want, cause i really didnt understand.. sometimes i have this problem understanding users

May 15th, 2004, 12:39 PM

tdw

Registered User

Join Date: May 2004

Location: London UK

Posts: 4

Time spent in forums: < 1 sec
Reputation Power: 0

try this

File (a portion of it)

Code:

Server_Port 8888
Max_Connect 100
Error_count 20

Code:

def load_from_file():
    f = open("c:\\myprog\\progdata.txt","r")
    r = f.readlines()
    f.close
    for line in r:
        var, val = line.split()[0], line.split()[1]

so for the first line read I have a variable called var containing Server_port and a variable called val containing 8888. From these I need to create a variable called Server_Port with the value 8888 for

Code:

def StartServer():
    server = HTTPServer((' ', Server_Port), RequestHandler)

In this case its an INI file, but not always, I don't want to have to list *all* the possible variable names within the prog itself so a dynamic method is preferable.

TIA

May 15th, 2004, 12:49 PM

xlordt

Only the strong survives!!.

Join Date: Feb 2003

Location: A World of wonders.

Posts: 5,573

Time spent in forums: 1 Month 11 h 9 m 33 sec
Reputation Power: 406

so you are saing that you are going to have data like so

Code:

Server_Port 8888
Max_Connect 100
Error_count 20

Server_Port 8000
Max_Connect 100
Error_count 20

just want to make sure i fully understand, as im not a python guru yet

May 15th, 2004, 01:15 PM

Strike

Contributing User

Join Date: Dec 2001

Location: Houston, TX

Posts: 383

Time spent in forums: 1 h 41 m 27 sec
Reputation Power: 12

What's wrong with having them in a dict? That's the easiest way (and probably the best way) to do it.

__________________
Debian - because life's too short for worrying.
Best. (Python.) IRC bot. ever.

May 15th, 2004, 01:15 PM

tdw

Registered User

Join Date: May 2004

Location: London UK

Posts: 4

Time spent in forums: < 1 sec
Reputation Power: 0

The file will look like that yes (but without duplicates

)

May 15th, 2004, 01:23 PM

xlordt

Only the strong survives!!.

Join Date: Feb 2003

Location: A World of wonders.

Posts: 5,573

Time spent in forums: 1 Month 11 h 9 m 33 sec
Reputation Power: 406

Quote:

Originally Posted by tdw

The file will look like that yes (but without duplicates

)

Ok give me a few min while i comeup with something for you

May 15th, 2004, 01:27 PM

tdw

Registered User

Join Date: May 2004

Location: London UK

Posts: 4

Time spent in forums: < 1 sec
Reputation Power: 0

Quote:

Originally Posted by Strike

What's wrong with having them in a dict? That's the easiest way (and probably the best way) to do it.

I'm beginning to think so too

Thanks All

May 15th, 2004, 02:38 PM

xlordt

Only the strong survives!!.

Join Date: Feb 2003

Location: A World of wonders.

Posts: 5,573

Time spent in forums: 1 Month 11 h 9 m 33 sec
Reputation Power: 406

ok i got this little sample here.. but cant get rid of them \n

see what you can do.. but it does give you the port numbers

Code:

for x in file('data.db'):
         lists  = x
         Server =  lists[lists.find('Server_Port'):20]
         print Server[Server.find(' '):]

#10

May 15th, 2004, 04:15 PM

DevCoach

Contributing User

Dev Shed Intermediate (1500 - 1999 posts)

Join Date: Feb 2004

Location: London, England

Posts: 1,585

Time spent in forums: 2 Weeks 4 Days 2 h 58 m 23 sec
Reputation Power: 1372

This was discussed in a thread here a few weeks ago.

You can assign them to the dictionary returned by the builtin function globals(), and they will become global variables.

Code:

def load_from_file():
    f = open("c:\\myprog\\progdata.txt","r")
    r = f.readlines()
    f.close
    for line in r:
        var, val = line.split()[0], line.split()[1]
        globals()[var] = val

However you cannot create local variables this way, since the locals() function creates a copy of the local namespace and any changes to it will have no effect. To create a local variable you have to use

Code:

exec "%s = %s" % (var, val)

instead.

You can also create an attribute on an object with

Code:

setattr(obj, var, val)

On the other hand, it may be simpler to use a dictionary, as others have said.

Dave - The Developers' Coach

How to dynamically assign variables

Developer Shed Advertisers and Affiliates