Python: issue with calling methods

Question

I'm new to Python and I've written a class for managing a simple phonebook. (I've removed the methods that aren't relevant to this post).

class Phonebook:
 def __init__(self):
 self.book = {}
 def newEntry(self, name, number):
 self.book[name] = number
 def findNumber(self, name):
 return self.book[name]
 def nameList(self):
 list = self.book.keys()
 list.sort()
 for k in list:
 print k, self.book[k]

My question concerns the last method, nameList, which prints the phonebook entries (name and phone no.) in alphabetical order. Originally, I tried the following:

 def nameList(self):
 list = self.book.keys()
 list.sort()
 for k in list:
 print k, findNumber(k)

However, this threw up a "NameError" global name 'findNumber' is not defined" error. Would someone be able to explain why this didn't work?

Thanks in advance.

• Mark Ransom: Please don't name your variables list, it's already the name of the built-in list type.

Answer 1

This doesn't work because findNumber is not a globally defined function. It's a method on your object, so to call it, you would need to invoke self.findNumber(k).

So your example would look like:

 def nameList(self):
 list = self.book.keys()
 list.sort()
 for k in list:
 print k, self.findNumber(k)

• Sam Mussmann: No problem! If this did solve your problem, could you mark my answer accepted? Thanks!
• Robincognito: Done. :) It wouldn't let me accept your answer before a few minutes had passed.

Answer 2

findNumber(k) should be accessed as self.findNumber(k) when inside class.

or as Phonebook.findNumber(self,k).

because a variable or function declared under a class becomes a class's attribute.

Answer 3

you need to add self to findNumber()

so it would become:

def nameList(self):
 list = self.book.keys()
 list.sort()
 for k in list:
 print k, self.findNumber(k)

else it doesn't know where findNumber is coming from because it is only defined in your class, or, self.