Python print objects design

Question

On the following classes, each object has it's own (customized) print function called pprint.

(There is more objects in the actual code than what's presented below).

class Device(object):
    """
    Device: a MAC address, a name (optional), an ip(s) (optional),
    and a list of Interface objects.
    """
    def __init__(self, ip='', name='', mac=''):

    def addIp(self, ip):

    def getInterface(self, name):

    def removeDuplicates(self):

    def pprint(self, disp=MORE):

    def toCSV(self, outputFolder=outputPath):


class Interface(object):
    """
    Interface: a name, a status and a set of Link objects.
    It can be physical (port) or virtual (interface).
    e.g: name  : BAGG1,
         status: TRUNK,
         links : [(vlan1, mac1), (vlan2, mac2), ...]
    """
    def __init__(self, name):
        self.name = name
        self.links = []
        self.status = ''

    def addLink(self, vlan='', destMAC=''):

    def getValues(self):

    def _removeDuplicates(self):

    def pprint(self, disp=MORE):

Among the following options, what is better/more efficient/more Pythonic ?

1. Put a pprint function inside each class (like above):
- Advantage: obj.pprint(args) is easy to use.
- Disadvantage: every object I want to print has its own pprint function, so it decreases code readability for what really matters in the class.
2. Have a dedicated Printer class:
```
class NetworkPrinter(object):        
    def __init__(self, obj):  

    def pprint(self, disp=MORE, keyList=None, filters=[], padding=20):

    def devicePrint(self, disp=MORE):

    def interfacePrint(self, disp=MORE):
```
Note: pprint will call the appropriate print function based on the type of the object.
- Advantage: Code is more organized.
- Disadvantage: Have to import the class, create a printer object and call it each time to get the pprint function: import Printer p = Printer() p.pprint(obj)
3. Have no dedicated Printer class:
```
def pprint(obj, disp=MORE, keyList=None, filters=[], padding=20):

def devicePrint(obj, disp=MORE):

def interfacePrint(obj, disp=MORE):
```
Note: pprint will call the appropriate print function based on the type of the object.
- Advantage: Don't have to instantiate any Printer object. Can call directly pprint(obj) for any object.
- Disadvantage: Code less organized and kind of messy.

I typically implement a __repr__ or a __str__ method. Then I can use standard "print" or "logging" functions. Seems more Pythonic to me. I guess this is most like your option 1. Option 2 and 3 mean that the Printer class has to have detailed knowledge of the implementation of the other classes, which seems like a violation of basic object oriented principles. But this is more of an opinion question which is typically frowned upon at SO. — RobertB
– RobertB, Commented Nov 3, 2015 at 18:31

Anton Zuenko · Accepted Answer · 2015-11-03 18:33:22Z

3

I'd suggest you to add __str__ method to each class definition and then print using standard builtin: print(class_instance). Internally, python calls __str__ to get a string representation of the instance.

answered Nov 3, 2015 at 18:33

Anton Zuenko

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1 Comment

JahMyst Over a year ago

Ok but my print functions have additional arguments like disp, filters, padding, ..., which allow me to customize the output. Is there a way to pass more arguments to print ?

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