feat: class tutorials

class/class_introduction.py

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+
+class Konto():
+    pass
+
+k1 = Konto()
+k2 = Konto()
+
+print(k1)
+print(k2)
+print(k1 is k2)

class/dataclass_tutorial.py

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+from dataclasses import dataclass
+
+@dataclass
+class Student:
+    name: str
+    nr: int
+    sem: int
+
+@dataclass
+class Rechteck:
+    breite: float
+    hoehe: float
+
+    def flaeche(self) -> float:
+        return self.breite * self.hoehe
+    
+# Validierung
+@dataclass
+class Produkt:
+    name: str
+    preis: float
+
+    def __post_init__(self):
+        if not self.name:
+            raise ValueError("...")
+        if self.preis < 0:
+            raise ValueError("...")

class/konto.py

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+class Konto():
+    def __init__(self, inhaber, saldo):
+        if not inhaber:
+            raise ValueError("Inhaber darf nicht leer sein")
+        if saldo < 0:
+            raise ValueError("Saldo darf nicht negativ sein")
+        self.inhaber = inhaber
+        self.saldo = saldo
+
+    def einzahlen(self, betrag):
+        self.saldo += betrag
+
+    def abheben(self, betrag):
+        self.saldo -= betrag
+
+k = Konto("Alice", 100)
+print(k.saldo)
+k.einzahlen(25)
+print(k.saldo)
+k.abheben(45)
+print(k.saldo)

class/repr_tutorial.py

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+class Konto:
+    def __init__ ( self , inhaber , saldo ) :
+        self . inhaber = inhaber
+        self . saldo = saldo
+    
+    def __repr__ ( self ) :
+        return f"Konto(inhaber = {self.inhaber!r}, saldo = {self.saldo!r})"
+    
+k = Konto ( " Alice " , 100.0)
+print ( k ) # Konto ( inhaber = Alice , saldo =100.0)

class/str_tutorial.py

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+class Konto:
+    def __init__ (self, inhaber, saldo):
+        self.inhaber = inhaber
+        self.saldo = saldo
+    
+    def __repr__(self):
+        return f"Konto(inhaber = {self.inhaber!r}, saldo = {self.saldo!r})"
+    
+    def __str__(self):
+        return f"Konto von {self.inhaber}: CHF {self.saldo:.2f}"
+    
+k = Konto ( " Alice " , 100.0)
+print(str(k))   # __str__
+print(repr(k))  # __repr__
+print(k)        # bevorzugt __str__ , sonst __repr__