python structs for dict of files

Question

This may be a newb question, but I'm a bit of newb with python, so here's what I'm trying to do...

I am using python2.7

I would like to assign a file path as a string into a dict in functionA, and then call this dict in functionB.

I looked at C-like structures in Python to try and use structs with no luck, possibly from a lack of understanding... The below sample is an excerpt from the link.

I also took a look at What are metaclasses in Python?, but I'm not sure if I understand metaclasses either.

So, how would I call assigned parameters in functionaA, within frunctionB such as:

class cstruct:
    path1 = ""
    path2 = ""
    path3 = ""


def functionA():
   path_to_a_file1 = os.path.join("/some/path/", "filename1.txt")
   path_to_a_file2 = os.path.join("/some/path/", "filename2.txt")
   path_to_a_file3 = os.path.join("/some/path/", "filename3.txt")

   obj = cstruct()
   obj.path1 = path_to_a_file1
   obj.path2 = path_to_a_file2
   obj.path3 = path_to_a_file3

   print("testing string here: ", obj.path1)
      # returns the path correctly here



# this is where things fall apart and the print doesn't return the string that I've tested with print(type(obj.path))
def functionB():
   obj = cstructs()
   print(obj.path1)
   print(obj.path2)
   print(obj.path3)

   print(type(obj.path))
      # returns <type 'str'>, which is what i want, but no path

Am I passing the parameters properly for the paths? If not, could someone please let me know what would be the right way to pass the string to be consumed?

Thanks!

Python doesn't have structs, instead, you would just use a class. Note, your class isn't defined properly. You have class-variables, and you want instance variables, and you probably want to define an appropriate constructor. Don't worry about metaclasses until you fully grasp the basics, you will almost never need a metaclass. — juanpa.arrivillaga, Apr 19 '20 at 22:00
@ArthurTacca a class is a perfectly reasonable thing to use here. Indeed, `dict` objects really shouldn't be used this way, they are mapping types, but the OP wants a sort of record type. — juanpa.arrivillaga, Apr 19 '20 at 22:01
Anyway, you create a new, empty `cstructs` objects: `obj = cstructs()` which is why you are seeing the behavior you are seeing. Again, you really should read up on the basics of classes/instances in Python, it is a core feature of the language. As an aside, you **really** should be using Python 3. — juanpa.arrivillaga, Apr 19 '20 at 22:03
I tried replacing the the `obj.path1 = path_to_a_file1` for `obj['path1'] = path_to_a_file1` and received an error: `cstruct instance has not attribute '__setitem__'`. Was this correct? — newb art online, Apr 19 '20 at 22:05
@newbartonline that isn't what the poster is referring to, they are suggesting you use a `dict` object, but using a custom class is actually a much better practice to begin with. You just need to understand how to actually use them. Note, **you aren't actually passing any parameters to `functionB`, and you didn't define it to take any parameters** — juanpa.arrivillaga, Apr 19 '20 at 22:06

score 0 · Accepted Answer · answered Apr 19 '20 at 22:11

You need to do something like this:

class Paths:
    def __init__(self, path1, path2, path3):
        self.path1 = path1
        self.path2 = path2
        self.path3 = path3

def functionA():
    path_to_a_file1 = os.path.join("/some/path/", "filename1.txt")
    path_to_a_file2 = os.path.join("/some/path/", "filename2.txt")
    path_to_a_file3 = os.path.join("/some/path/", "filename3.txt")

    obj = Paths(path_to_a_file1, path_to_a_file2, path_to_a_file3)
    return obj

def functionB(paths): # should take a parameter
   # obj = cstructs() don't do this! This would create a *new empty object*
   print(paths.path1)
   print(paths.path2)
   print(paths.path3)

   print(type(paths.path))


paths = functionA()
functionB(paths) # pass the argument

In any case, you really should take the time to read the official tutorial on classes. And you really should be using Python 3, Python 2 is passed its end of life.

thank you... i would try to use 3.x, but stuck with 2.7 for this. :) — newb art online, Apr 19 '20 at 22:21
@juarnpa.arrivillaga... thanks again! i went with just init a `list = [None]*3]` at the top of the program and filling the data in `functionaA`, and later calling in `functionB`... i really didn't want to assign data types into the functions A and B, since they have types for other purpose, which is why i was going with the struct route (i should have been explicit in my write up, sorry)... your info helped a lot though, thanks. :) — newb art online, Apr 19 '20 at 23:51

python structs for dict of files

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