[Tutor] Global var not defined?
Could use some help with this. Python 2.4.3 on RHEL 5.x.
In the functions file that gets imported:
def append_customer(line_list):
global customers
cust = line_list[0] // list with Customer info in [0]
cust = clean_word(cust) // Trims white space
if len(cust) and cust not in customers:
host_list[cust] = {}
customers.append(cust)
In the calling file:
import functions
import sys
customers = []
.
.
.
for line in input_file:
line = line.strip()
if not len(line):
continue
line_list = line.split(',')
functions.append_customer(line_list)
Error message:
Traceback (most recent call last):
File ./host_tools.py, line 55, in ?
functions.append_customer(line_list)
File /home/lhall/lang/functions.py, line 27, in append_customer
if len(cust) and cust not in customers:
NameError: global name 'customers' is not defined
--
Mind on a Mission http://leamhall.blogspot.com/
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Re: [Tutor] Global var not defined?
On 27/08/13 18:58, leam hall wrote:
def append_customer(line_list):
global customers
cust = line_list[0] // list with Customer info in [0]
cust = clean_word(cust) // Trims white space
if len(cust) and cust not in customers:
host_list[cust] = {}
customers.append(cust)
In Python global only applies to the local file.
Thus customers needs to be at the global level in
functions.py.
But since its a bad use of globals it would be better to just get the
function to return the value and do the append in the top level file...
BTW the line
host_list[cust] = {}
Makes no sense since you are adding an empty dictionary to a variable
that doesn't exist so you should get an error. I assume you have
simplified the code somewhat?
In the calling file:
import functions
import sys
customers = []
.
.
for line in input_file:
line = line.strip()
if not len(line):
continue
line_list = line.split(',')
functions.append_customer(line_list)
customers.append(functions.get_customer(line_list, customers))
Avoids any need for globals.
Personally I'd move the line split into the function so your loop looks
like:
for line in input_file:
line = line.strip()
if line:
customers.append(functions.get_customer(line_list, customers))
Alternatively I'd put the customers list into a module called customer
and move the customer functions into that module. And then it looks
like I might have a Customer class emerging... And maybe the code above
would become a class method:
Customer.readFromFile(aFile) - [cust1, cust2, ...]
Just a thought...
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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Re: [Tutor] Global var not defined?
leam hall wrote:
Could use some help with this. Python 2.4.3 on RHEL 5.x.
In the functions file that gets imported:
def append_customer(line_list):
global customers
cust = line_list[0] // list with Customer info in [0]
cust = clean_word(cust) // Trims white space
if len(cust) and cust not in customers:
host_list[cust] = {}
customers.append(cust)
In the calling file:
import functions
import sys
customers = []
.
.
.
for line in input_file:
line = line.strip()
if not len(line):
continue
line_list = line.split(',')
functions.append_customer(line_list)
Error message:
Traceback (most recent call last):
File ./host_tools.py, line 55, in ?
functions.append_customer(line_list)
File /home/lhall/lang/functions.py, line 27, in append_customer
if len(cust) and cust not in customers:
NameError: global name 'customers' is not defined
The problem is because customers needs to be defined
in the module with the append_customers. Global as
written refers to module level variables.
Some (possible and untested) methods to get around this are:
1. pass in customers as an argument
2. use globals()?
3. add it to functions module `functions.customers = customers`.
~Ramit
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Re: [Tutor] Global var not defined?
On 27/08/13 19:50, leam hall wrote:
Well, I'm happy to change things but my python is only so good. And much
of that is based off of shell programming.
You will need to change something because what you have won;t work.
The question is what to change?
What the data looks like is fairly simple. I have a spreadsheet of host
information. Customer 'Alan' may have a dozen or so servers and customer
Ramit has another dozen or two.
So abstracting that you have several customer objects each containing
a list(or dict?) of servers. Servers in turn have numerous attributes:
name, role, ip, environ etc...
When I print these out they will be
sorted by customer but rolled into a single file.
So the customer objects have a method that prints to a file.
That's the OOP approach, but you can do it without classes
if you want, its just a bit more effort on the readability
and coding front.
The line host_list[cust] = {} creates the customer dictionary if that
customer doesn't exist.
It may be better to look at the get() method of dictionaries for that.
But the problem I highlighted was that the top level host_list
dictionary didn't exist in your code. You need to initialize
it before you can access the cust key.
host_list = {}
.
.
.
host_list.get(cust, {})
Then there's a host key with multiple layers:
host_list['alan']['webserver']['ip'] = '12.23.34.45'
host_list['alan']['webserver']['environ'] = 'Dev'
Make sense? As I do not know a lot about classes I'm not sure they are
better in this case than a multi-level dictionary.
A class is effectively a dictionary inside so its very similar.
Using my OOP suggestion above this would translate to something like:
alan.servers['webserver'].ip = '12.23.34.45
Which you find more readable is a matter of taste!
There are some other advantages to the OOP approach but
they are not critical here.
The data does not get altered, just organized.
That doesn't make much difference in this case.
The simplest solution to get it working is probably just
to move the customers list into the functions module.
In the longer term the other options might prove more beneficial.
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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Re: [Tutor] Global var not defined?
On 28/08/13 03:58, leam hall wrote: Could use some help with this. Python 2.4.3 on RHEL 5.x. In the functions file that gets imported: def append_customer(line_list): global customers Globals are not globally global, they are global to the module. Otherwise variables defined in module X would stomp all over variables defined in module Y, unpredictably depending on the order than modules were imported. In the calling file: import functions import sys customers = [] This cannot work, because it belongs to a different namespace (module). Just pass customers as an explicit parameter to append_customer, and then google for Global variables considered harmful. If you absolutely must emulate COBOL programmers of the 1970s and insist on using globals, write: functions.customers = [] instead. -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
