'local' var in module

[Andreas Lobinger]

Aloha,

i'm i little bit confused by the following behaviour...

lobingera@sibyl: cat flip.py
import random

paras = { 'flength' : 22,
'cset' : 'abcdefghijkl' }
rstate = 1

def f():
random.seed(rstate)
s = list()

for i in range(paras['flength']):
s.append(random.choice(paras['cset']))

return "".join(s)

def g():
random.seed(rstate)
s = list()

for i in range(paras['flength']):
s.append(random.choice(paras['cset']))

rstate = random.getseed()
return "".join(s)

I try to save the state of the random module locally in flip.
I also have other parameters (paras) in the module.

lobingera@sibyl: python
Python 2.2.2 (#3, Apr 10 2003, 17:06:52)
[GCC 2.95.2 19991024 (release)] on sunos5
Type "help", "copyright", "credits" or "license" for more information.Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "flip.py", line 17, in g
random.seed(rstate)
UnboundLocalError: local variable 'rstate' referenced before assignmentSomehow 'rstate' is readable in f, but not in g, but paras is?

Wishing a happy day
LOBI

 

[Aaron Bingham]

Aloha,

i'm i little bit confused by the following behaviour...

lobingera@sibyl: cat flip.py

[working code deleted]

If you assign to a variable inside a function, it will define a variable
local to that function, unless you explicity declare that variable as a
global, like so:

def g():

global rstate

random.seed(rstate)
s = list()

for i in range(paras['flength']):
s.append(random.choice(paras['cset']))

rstate = random.getseed()
return "".join(s)

Aaron

 

[Josiah Carlson]

lobingera@sibyl: cat flip.py
import random

paras = { 'flength' : 22,
'cset' : 'abcdefghijkl' }
rstate = 1

def f():
random.seed(rstate)
s = list()

for i in range(paras['flength']):
s.append(random.choice(paras['cset']))

return "".join(s)

When you are only reading things, Python will pull variables from the
local or global scope as necessary.

def g():
random.seed(rstate)
s = list()

for i in range(paras['flength']):
s.append(random.choice(paras['cset']))

rstate = random.getseed()
return "".join(s)

If you try to write to a variable in a scope, Python believes that the
variable is local to this scope, so doesn't attempt to fetch it from
globals, and will only write to the local copy.

That is, unless you include the 'global' keyword. Add:
global rstate
to g() and watch everything work the way you expect.

- Josiah

 

[Mel Wilson]

Aloha,

i'm i little bit confused by the following behaviour...

lobingera@sibyl: cat flip.py
import random

paras = { 'flength' : 22,
'cset' : 'abcdefghijkl' }
rstate = 1

def f():
random.seed(rstate)
s = list()

for i in range(paras['flength']):
s.append(random.choice(paras['cset']))

return "".join(s)

def g():
random.seed(rstate)
s = list()

for i in range(paras['flength']):
s.append(random.choice(paras['cset']))

rstate = random.getseed()
return "".join(s)
[ ... ]
Somehow 'rstate' is readable in f, but not in g, but paras is?

It's the `rstate = random.getseed()` in g, which forces
rstate to be local. Put a `global rstate` in g and you
solve the visiblity problem.

Regards. Mel.