How to alter return function/change variable using a function?

I was wondering how I can have a changing variable from a function.

I attempted:

class Text():
  File=open("SomeFile.txt", "r")
  MyText=(File.read()+MoreText)
  def AddMoreText():
    MoreText=("This is some more text")

before realising that I needed to run the MyText variable again which I'm not sure how to do.

I intend to call this text by running something along the lines of print(Text.MyText) which doesn't update after running Text.AddMoreText()

I then tried:

class Text():
  global MoreText
  File=open("SomeFile.txt", "r")
  def ChangeTheText():
    return(File.read()+MoreText)
  MyText=ChangeTheText()
  def AddMoreText():
    MoreText=("This is some more text")

What I didn't know was that the return function preserves its value so when I ran print(Text.MyText) Text.AddMoreText() print(Text.MyText) it displayed the same text twice.

Solution

I think you want something like:

class Text:
    def __init__(self):
        self.parts = []
        with open('SomeFile.txt', 'r') as contents:
            self.parts.append(contents.read())
        self.parts.append('More text')

    def add_more_text(self, text):
        self.parts.append(text)

    @property
    def my_text(self):
        return ''.join(self.parts)

This makes .my_text a dynamic property that will be re-computed each time .my_text is retreived.