Python Forum

Hello I am receiving these messages when running my code:

Error:
File "/home/leopoldo/cpu.py", line 28, in process_instructions
    instruction = self.identify_instruction (byte)
  File "/home/leopoldo/cpu.py", line 18, in identify_instruction
    instruction = BPLInstruction (byte)
NameError: global name 'BPLInstruction' is not defined

The code:

def process_instructions (self):
		counter=0
		for byte in self.rom.data_bytes:
			byte = self.rom.get_byte (self.pc)
			instruction = self.identify_instruction (byte)
			if instruction is None:
				raise Exception ("Instruction not found")
			instruction.process ()
			print ("self.pc, antes: ", self.pc)
			self.pc+= instruction.instruction_length
			print ("counter: ", counter)
			print ("self.pc, depois: ", self.pc)
			print ("")
			counter = counter + 1

def identify_instruction (self, byte):
		if byte==0x78:	
			instruction = LDAInstruction (byte)
		elif byte==0xD8:
			instruction = SEIInstruction (byte)
		elif byte==0xA9:
			instruction = CLDInstruction (byte)
		elif byte==0x10:
			instruction = BPLInstruction (byte)
		else:
			instruction = None
		return instruction

class LDAInstruction (Instruction):
	def process (self):
		print ("Identifier Byte: LDAInstruction:",hex (self.identity_byte), self.identity_byte )
	instruction_length = 2

class SEIInstruction (Instruction):
	def process (self):
		print ("Identifier Byte: SEIInstruction:",hex (self.identity_byte), self.identity_byte)
	instruction_length = 1

class CLDInstruction (Instruction):
	def process (self):
		print ("Identifier Byte: CLDInstruction:",hex (self.identity_byte), self.identity_byte)
	instruction_length = 1

class BPLinstruction (Instruction):
	def process (self):
		print ("Identifier Byte: BPLinstruction:",hex (self.identity_byte), self.identity_byte)
	instruction_length = 1

I can't identify the source of trouble because I see no difference between the code related to BPL, whether is its class definition or its elif clause on "identify_instruction" to the others instruction's code.

So I don't see what is not defined there, especially when python does not complain about any other instruction. Thanks for the help.

in class definition, name is BPLinstruction (small i)
when instantiated you use capital I

(Oct-21-2019, 12:51 AM)Larz60+ Wrote: [ -> ]in class definition, name is BPLinstruction (small i)
when instantiated you use capital I

Thanks. I did changed it to

class BPLInstruction (Instruction):

instead of

class BPLinstruction (Instruction):

Nonetheless, the error message continued, exactly as before. What else can be?

it's line 18!
print ("Identifier Byte: BPLinstruction:",hex (self.identity_byte), self.identity_byte)

(Oct-23-2019, 11:29 PM)Larz60+ Wrote: [ -> ]it's line 18!
print ("Identifier Byte: BPLinstruction:",hex (self.identity_byte), self.identity_byte)

Between the quotes? Well, I changed it but the error remains.

show your full code

I somewhat was able to fix it through the correction of a logical bug.

The code that fix it is:

        if byte==0x78:	
			instruction = SEIInstruction (byte)
		elif byte==0xD8:
			instruction = CLDInstruction (byte)
		elif byte==0xA9:
			instruction = LDAInstruction (byte)

and not

def identify_instruction (self, byte):
		if byte==0x78:	
			instruction = LDAInstruction (byte)
		elif byte==0xD8:
			instruction = SEIInstruction (byte)
		elif byte==0xA9:
			instruction = CLDInstruction (byte)

However I added code for a new instruction with

class STAabsInstruction (Instruction):
	def process (self):
		print ("Identifier Byte: STAabsInstruction:",hex (self.identity_byte), self.identity_byte )
	instruction_length = 3

and code to deal with it

elif byte==0x8D:
			instruction = STAabsInstruction (byte)

and now I am receiving

Error:
File "/home/leopoldo/cpu.py", line 32, in process_instructions
    instruction = self.identify_instruction (byte)
  File "/home/leopoldo/cpu.py", line 20, in identify_instruction
    instruction = STAabsInstruction (byte)
NameError: global name 'STAabsInstruction' is not defined

Full code for the two classes that use Instructions:

from rom import ROM
from instruction import LDAInstruction, SEIInstruction, CLDInstruction

class CPU (object):
	def __init__(self, rom_bytes):
		self.registers = []
		self.rom = ROM (rom_bytes)
		self.pc = 0		

	def identify_instruction (self, byte):
		if byte==0x78:	
			instruction = SEIInstruction (byte)
		elif byte==0xD8:
			instruction = CLDInstruction (byte)
		elif byte==0xA9:
			instruction = LDAInstruction (byte)
		elif byte==0x10:
			instruction = BPLInstruction (byte)
		elif byte==0x8D:
			instruction = STAabsInstruction (byte)
		else:
			instruction = None
		return instruction
		

	def process_instructions (self):
		counter=0
		for byte in self.rom.data_bytes:
			byte = self.rom.get_byte (self.pc)
			print ("self.pc, antes: ", self.pc)
			print ("byte: ", hex (byte), byte)
			instruction = self.identify_instruction (byte)
			if instruction is None:
				raise Exception ("Instruction not found")
			instruction.process ()
			self.pc+= instruction.instruction_length
			print ("counter: ", counter)
			print ("self.pc, depois: ", self.pc)
			print ("")
			if self.pc>=5:
				break
			

from abc import ABCMeta, abstractmethod, abstractproperty

class Instruction (object):
	__metaclass_ = ABCMeta
		
	def __init__ (self,identification_byte):
		self.identity_byte = identification_byte

	@abstractproperty
	def instruction_length (self):
		return 1

	@abstractmethod
	def process (self):
		pass
		
class SEIInstruction (Instruction):
	def process (self):
		print ("Identifier Byte: SEIInstruction:",hex (self.identity_byte), self.identity_byte)
	instruction_length = 1

class CLDInstruction (Instruction):
	def process (self):
		print ("Identifier Byte: CLDInstruction:",hex (self.identity_byte), self.identity_byte)
	instruction_length = 1

class LDAInstruction (Instruction):
	def process (self):
		print ("Identifier Byte: LDAInstruction:",hex (self.identity_byte), self.identity_byte )
	instruction_length = 2

class STAabsInstruction (Instruction):
	def process (self):
		print ("Identifier Byte: STAabsInstruction:",hex (self.identity_byte), self.identity_byte )
	instruction_length = 3

I assume these classes are in separate files, and each named the same as the class that they hold? (you don't show the module names)
on line 2 of cpu.py, you don't import STAabsInstruction, thus the error on line 20.