Python, class initialization with one value

Question

I have a class which takes two numbers and prints them in a list

class Numbers():
 def __init__(self, l, r):
 self.l = l
 self.r = r
 def __str__(self):
 print([self.l, self.r])

ex:

N = Numbers(1, 3) #[1, 3]

Now, I need to extend the class so that it can be initialized with only one value

N2 = Numbers(2) #[2, 2]

Right now I'm a bit clueless on how to proceed, any help is appreciated

• user2357112: __str__ is supposed to return a string, not print stuff.
• Joseph D.: This might be helpful? stackoverflow.com/questions/13382774/…

Answer 1

You can simply use a default parameter:

class Numbers():
 def __init__(self, l, r=None):
 self.l = l
 if r is None:
 self.r = l
 else:
 self.r = r
 def __str__(self):
 return str([self.l, self.r])
print(Numbers(1, 2))
# [1, 2]
print(Numbers(3))
# [3, 3]

Answer 2

How about this:

def __init__(self, l, r = None):
 self.l = l
 if r is None:
 self.r = l
 else:
 self.r = r

As others already pointed out, you'll need to modify your __str__ method as well, to be something like this:

def __str__(self):
 return str(self.l) + "," + str(self.r)

Answer 3

Try this:

class Numbers:
 def __init__(self, l, r=None):
 self.l = l
 self.r = r if r else l
 def __str__(self):
 return str([self.l, self.r])

ex:

n1 = Numbers(3, 5)
print(n1) # [3, 5]
n2 = Numbers(2)
print(n2) # [2, 2]