diff --git a/m6502/memory.py b/m6502/memory.py
index 01f4894..133dac2 100644
--- a/m6502/memory.py
+++ b/m6502/memory.py
@@ -13,9 +13,9 @@ def __init__(self, size: int = None) -> None:
         """
         if size is None:
             size = 0xFFFF
-        if size < 0x0200:
+        elif size < 0x0200:
             raise ValueError("Memory size is not valid")
-        if size > 0xFFFF:
+        elif size > 0xFFFF:
             raise ValueError("Memory size is not valid")
         self.size = size
         self.memory = [0] * self.size
@@ -27,7 +27,7 @@ def __getitem__(self, address: int) -> int:
         :param address: The address to read from
         :return: The value at the specified address
         """
-        if 0x0000 < address > 0xFFFF:
+        if 0 > address or address > 0xFFFF:
             raise ValueError("Memory address is not valid")
         return self.memory[address]
 
@@ -39,7 +39,7 @@ def __setitem__(self, address: int, value: int) -> int:
         :param value: The value to write to the address
         :return: None
         """
-        if 0x0000 < address > 0xFFFF:
+        if 0 > address or address > 0xFFFF:
             raise ValueError("Memory address is not valid")
         if value.bit_length() > 8:
             raise ValueError("Value too large")
diff --git a/m6502/processor.py b/m6502/processor.py
index c52923e..19771b1 100644
--- a/m6502/processor.py
+++ b/m6502/processor.py
@@ -234,7 +234,9 @@ def execute(self, cycles: int = 0) -> None:
         """
         while (self.cycles < cycles) or (cycles == 0):
             opcode = self.fetch_byte()
-            eval("self.ins_" + self.OPCODES[opcode] + "_" + self.ADDRESSING[opcode] + "()")  # noqa: PLW0123
+            name = f"ins_{self.OPCODES[opcode]}_{self.ADDRESSING[opcode]}"
+            method = getattr(self, name)
+            method()
 
     def ins_nop_imp(self) -> None:
         """