Methods and self

What a session covers

The tutor works through these with you, in conversation and code. A session ends when you have shown them, not when a video does.

1. Explain what self is and how Python fills it in when a method is called
2. Write methods that read and change the instance's own data
3. Spot the missing self behind "takes 1 positional argument but 2 were given"

In practice

A few lines that show Methods and self doing its job.

class Account:
    def __init__(self, balance=0):
        self.balance = balance

    def withdraw(self, amount):
        if amount > self.balance:
            raise ValueError("insufficient funds")
        self.balance -= amount
        return self.balance

acct = Account(100)
print(acct.withdraw(30))       # 70

The common mistake

What to know first

Your roadmap puts these before Methods and self, unless you already know them.

• Classes and instances

How it stays learned

Once a session shows you understand Methods and self, it comes back for review. Each review takes a minute and tells the memory model how well you still know it.

1. Day 3First recall, while it is fresh
2. Day 7Second, a week on
3. Day 18Last, when it has settled

Where it leads

Topics that build on Methods and self.

• Inheritance