Python 3：为什么我会收到 AttributeError？

Question

我是运行 Python 3，我收到以下错误：

AttributeError: 'AssemblyParser' object has no attribute 'hasMoreCommands'

这是引发错误的代码：

import sys
from Parser import AssemblyParser
from Code import Code

parser = AssemblyParser(sys.argv[1])
translator = Code()

out_file = str(sys.argv[1]).split(".")
out_file = str(out_file[:1]) + ".hack"

with open(out_file, 'w', encoding='utf-8') as f:
    while parser.hasMoreCommands():
        parser.advance()
        if parser.commandType() == "A_COMMAND":
            dec_num = parser.symbol()
            binary = "{0:b}".format(dec_num)
        elif parser.commandType() == "C_COMMAND":
            default_bits = "111"
            comp_bits += translator.comp(parser.comp())
            dest_bits += translator.dest(parser.dest())
            jump_bits += translator.jump(parser.jump())
            binary = default_bits + comp_bits + dest_bits + jump_bits
        assert len(binary) == 16
        f.write(binary)

这是我的 Parser.py 文件：

class AssemblyParser:
"""
Encapsulates access to the input code. Reads an assembly language command, 
parses it, and provides convenient access to the command's components (fields and symbols).
In addition, removes all whitespace and comments.
"""

def __init__(self, input_file):
    self.current_command = ""
    self.next_command = ""
    with open(input_file,"r+", encoding='utf-8') as f:
        for l in f:
            line = "".join(l.split()) # Remove whitespace from the line
            line = line.split('//') # Removes any comments from the line
            clean_line = line[0]
            if clean_line.strip(): # Removes any blank lines
                f.write(clean_line)
        next_command = f.readline()


def __hasMoreCommands__(self):
    if self.next_command:
        return true
    return false


def __advance__(self):
    with open(input_file, encoding='utf-8') as f:
        self.current_command = self.next_command
        self.next_command = f.readline()


def __commandType__(self):
    char_1 = self.current_command[:1]
    if char_1 == "@":
        return "A_COMMAND"
    elif char_1 == "(":
        return "L_COMMAND"
    else:
        return "C_COMMAND"


def __symbol__(self):
    assert self.commandType() == ("A_COMMAND" or "L_COMMAND")

    if self.commandType() == "A_COMMAND":
        symbol = str(symbol[1:])
    else:
        symbol = str(symbol[1:len(symbol)-1])
    return str(symbol)


def __dest__(self):
    assert self.commandType() == "C_COMMAND"

    if "=" in self.current_command:
        temp = self.current_command.split("=")
        return str(temp[:1])
    else:
        return ""


def __comp__(self):
    assert self.commandType() == "C_COMMAND"

    temp = self.current_command

    if "=" in temp:
        temp = temp.split("=")
        temp = str(temp[1:])
    if ";" in temp:
        temp = temp.split(";")
        temp = str(temp[:1])
    return temp


def __jump__(self):
    assert self.commandType() == "C_COMMAND"

    if ";" in self.current_command:
        temp = self.current_command.split(";")
        return str(temp[1:])
    else:
        return ""

我真的不知道为什么会出现这个错误，我已经查看了导入文档，但我越来越糊涂了。我是 Python 的新手。谁能解释这个错误？

谢谢。

Answer 1

嗯。名称为 hasMoreCommand 的 Parser 模块中似乎没有函数。那里的功能以下划线开头并以下划线结尾。

Answer 2

两个前导和尾随下划线用于标识 "magic" 属性。你不能用它来创建你自己的，因为它们只引用了预先存在的方法。

以下是您可能想要的：

hasMoreCommands():

如果您有多个类具有此功能，请改用名称修改：

_hasMoreCommands():

参见：

并且：http://www.rafekettler.com/magicmethods.html

Python 3：为什么我会收到 AttributeError？

Python 3: Why am I getting an AttributeError?

python

python-import

python-3.x