CODEWITHSUNDEEP
pythonclass
PythonJin
PythonJin

Reputation: 4134

Calling a class function inside of __init__

I'm writing some code that takes a filename, opens the file, and parses out some data. I'd like to do this in a class. The following code works:

class MyClass():
    def __init__(self, filename):
        self.filename = filename 

        self.stat1 = None
        self.stat2 = None
        self.stat3 = None
        self.stat4 = None
        self.stat5 = None

        def parse_file():
            #do some parsing
            self.stat1 = result_from_parse1
            self.stat2 = result_from_parse2
            self.stat3 = result_from_parse3
            self.stat4 = result_from_parse4
            self.stat5 = result_from_parse5

        parse_file()

But it involves me putting all of the parsing machinery in the scope of the __init__ function for my class. That looks fine now for this simplified code, but the function parse_file has quite a few levels of indention as well. I'd prefer to define the function parse_file() as a class function like below:

class MyClass():
    def __init__(self, filename):
        self.filename = filename 

        self.stat1 = None
        self.stat2 = None
        self.stat3 = None
        self.stat4 = None
        self.stat5 = None
        parse_file()

    def parse_file():
        #do some parsing
        self.stat1 = result_from_parse1
        self.stat2 = result_from_parse2
        self.stat3 = result_from_parse3
        self.stat4 = result_from_parse4
        self.stat5 = result_from_parse5

Of course this code doesn't work because the function parse_file() is not within the scope of the __init__ function. Is there a way to call a class function from within __init__ of that class? Or am I thinking about this the wrong way?

Upvotes: 227

Views: 327023

Answers (6)

Lewis Diamond
Lewis Diamond

Reputation: 25021

Call the function in this way:

self.parse_file()

You also need to define your parse_file() function like this:

def parse_file(self):

The parse_file method has to be bound to an object upon calling it (because it's not a static method). This is done by calling the function on an instance of the object, in your case the instance is self.

Upvotes: 308

Paritosh Singh
Paritosh Singh

Reputation: 6404

If I'm not wrong, both functions are part of your class, you should use it like this:

class MyClass():
    def __init__(self, filename):
        self.filename = filename 

        self.stat1 = None
        self.stat2 = None
        self.stat3 = None
        self.stat4 = None
        self.stat5 = None
        self.parse_file()

    def parse_file(self):
        #do some parsing
        self.stat1 = result_from_parse1
        self.stat2 = result_from_parse2
        self.stat3 = result_from_parse3
        self.stat4 = result_from_parse4
        self.stat5 = result_from_parse5

replace your line:

parse_file()

with:

self.parse_file()

Upvotes: 62

Ionut Hulub
Ionut Hulub

Reputation: 6326

You must declare parse_file like this; def parse_file(self). The "self" parameter is a hidden parameter in most languages, but not in python. You must add it to the definition of all that methods that belong to a class. Then you can call the function from any method inside the class using self.parse_file

your final program is going to look like this:

class MyClass():
  def __init__(self, filename):
      self.filename = filename 

      self.stat1 = None
      self.stat2 = None
      self.stat3 = None
      self.stat4 = None
      self.stat5 = None
      self.parse_file()

  def parse_file(self):
      #do some parsing
      self.stat1 = result_from_parse1
      self.stat2 = result_from_parse2
      self.stat3 = result_from_parse3
      self.stat4 = result_from_parse4
      self.stat5 = result_from_parse5

Upvotes: 1

Teo Klestrup Röijezon
Teo Klestrup Röijezon

Reputation: 5257

In parse_file, take the self argument (just like in __init__). If there's any other context you need then just pass it as additional arguments as usual.

Upvotes: 0

unutbu
unutbu

Reputation: 880877

How about:

class MyClass(object):
    def __init__(self, filename):
        self.filename = filename 
        self.stats = parse_file(filename)

def parse_file(filename):
    #do some parsing
    return results_from_parse

By the way, if you have variables named stat1, stat2, etc., the situation is begging for a tuple: stats = (...).

So let parse_file return a tuple, and store the tuple in self.stats.

Then, for example, you can access what used to be called stat3 with self.stats[2].

Upvotes: 18

Zed
Zed

Reputation: 5921

I think that your problem is actually with not correctly indenting init function.It should be like this

class MyClass():
     def __init__(self, filename):
          pass

     def parse_file():
          pass

Upvotes: -15

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