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Python Kata #4: Hello Mars!

Me and my friends like to travel to other planets. To keep track on which planets we visited I created a Python VisitTracker class. 

class VisitTracker:
  visited = []

  def __init__(self, name):
    self.name = name

  def visit(self, place):
    if place not in self.visited:
      self.visited.append(place)

  def list(self):
    print("====== " + self.name + "'s visits ======")
    print(self.visited)

I put all the Python source code in an Jupyter Notebook (I made it available for you as GitHub gist) and started using it. Added recent planetary visits John and Jane made:

  1. John visited Saturn together with Jane
  2. John visited Mars
  3. Jane visited Jupiter

Here is how I tracked this:

johns_visits = VisitTracker('John')
janes_visits = VisitTracker('Jane')

#1 John visited Saturn together with Jane
johns_visits.visit('Saturn')
janes_visits.visit('Saturn')

#2 John visited Mars
johns_visits.visit('Mars')
johns_visits.list()

#3 Jane visited Jupiter
janes_visits.visit('Jupiter')
janes_visits.list()

And the output was not quite what I was expecting:

====== John's visits ======
['Saturn', 'Mars']
====== Jane's visits ======
['Saturn', 'Mars', 'Jupiter']

I was expecting:

====== John's visits ======
['Saturn', 'Mars']
====== Jane's visits ======
['Saturn', 'Jupiter']

If you do not believe me - check the Jupyter Notebook with the Python code and the results in Colab.

What went wrong?