Python:函数不带参数 [英] Python:Function takes no arguments

问题描述

运行此代码时，我收到错误消息:

File "Start.py", line 22, in <module>
  c.lo()
TypeError: lo() takes no arguments (1 given)

我不知道为什么我会收到此错误，有人可以解释一下吗? 我知道这是说我在调用该函数时输入了一个参数，但我不明白为什么会这样?

如果有人可以阐明这个问题，那就太好了.

import subprocess as sp
import Tkinter as Tk
from Tkinter import *
root = Tk()
text = Text(root)

class Console:
    def Start():
        proc = sp.Popen(["java", "-Xmx1536M", "-Xms1536M", "-jar", ".jar"],stdin=sp.PIPE,stdout=sp.PIPE,)
    def lo():
        while True:
            line = proc.stdout.readline()
            text.insert(INSERT,line)
            text.pack()
            if (line == "Read Time Out"):
                proc.stdin.write('stop')
            if (line == "Unloading Dimension"):
                text.insert(INSERT,"Ready for command")
                text.pack()

c = Console()
c.Start()
c.lo()
root.mainloop()

简而言之，这是因为lo()是类Console的方法，该方法始终将实例作为第一个参数传递.因此，lo()必须定义一个参数(通常称为self)来保存该参数:

class Console:
    def start(self): # functions and methods should have lowercase names
        self.proc = sp.Popen(...)
    def lo(self):
        line = self.proc.stdout.readline()
        ...

您的Start()通话效果很好，我感到很惊讶；它有同样的问题.

When I run this code I get the error message:

File "Start.py", line 22, in <module>
  c.lo()
TypeError: lo() takes no arguments (1 given)

I don't know exactly why I am getting this error could someone please explain? I know it's saying that I put an argument when calling that function but I don't understand why that is?

If someone could shed some light on this issue that would be great.

import subprocess as sp
import Tkinter as Tk
from Tkinter import *
root = Tk()
text = Text(root)

class Console:
    def Start():
        proc = sp.Popen(["java", "-Xmx1536M", "-Xms1536M", "-jar", ".jar"],stdin=sp.PIPE,stdout=sp.PIPE,)
    def lo():
        while True:
            line = proc.stdout.readline()
            text.insert(INSERT,line)
            text.pack()
            if (line == "Read Time Out"):
                proc.stdin.write('stop')
            if (line == "Unloading Dimension"):
                text.insert(INSERT,"Ready for command")
                text.pack()

c = Console()
c.Start()
c.lo()
root.mainloop()

解决方案

In short, that is because lo() is a method of the class Console which is always passed the instance as first argument. So lo() must define a parameter (mostly called self) to hold that argument:

class Console:
    def start(self): # functions and methods should have lowercase names
        self.proc = sp.Popen(...)
    def lo(self):
        line = self.proc.stdout.readline()
        ...

I am surprised that your Start() call worked; it has the same issue.

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