如何将“stdout”重定向到标签小部件？

Question

我正在尝试将stdout重定向到一个标签小部件。目标是将脚本中的所有Python打印内容“打印”到标签中。

但是当我点击 BUTTON1 时，什么也没有发生...

这是我的代码：

from Tkinter import *
import sys
import tkMessageBox


class App:

    def __init__(self, master):

        self.frame = Frame(master, borderwidth=5, relief=RIDGE)
        self.frame.grid()

        class IORedirector(object):
            def __init__(self,TEXT_INFO):
                self.TEXT_INFO = TEXT_INFO

        class StdoutRedirector(IORedirector):
            def write(self,str):
                self.TEXT_INFO.config(text=str)

        self.TEXT_HEADER = self.text_intro = Label(self.frame, bg="lightblue",text="MY SUPER PROGRAMM") ## HEADER TEXT
        self.TEXT_HEADER.grid(row=0, column=0, columnspan=2, sticky=W+E+N+S)

        self.MENU = Frame(self.frame, borderwidth=5, relief=RIDGE, height=12) 

        self.MENU.grid(row=1, column=0, sticky=N)

        self.button = Button(self.MENU, text="QUIT", fg="red", bg="red", command=self.frame.quit)
        self.button.grid(row=4, column=0)

        self.BUTTON1 = Button(self.MENU, text="BUTTON1", command=self.BUTTON1_CMD)
        self.BUTTON1.grid(row=0, column=0,sticky=W+E)

        self.TEXT_INFO = Label(self.frame, height=12, width=40, text="I WANT TO SEE THE STDOUT OUTPUT HERE", bg="grey",borderwidth=5, relief=RIDGE)
        self.TEXT_INFO.grid(row=1, column=1)

        sys.stdout = StdoutRedirector(self.TEXT_INFO)

    def BUTTON1_CMD(self):
        print "TEST NUMBER ONE"
        print "TEST NUMBER TWO"


root = Tk()
app = App(root)
root.mainloop()

- user1422695

Answer 1

你没有看到设置的文本是因为它在正确设置了一小段时间后立即被设置为空。这是因为print语句在打印完后向stdout发送了一个换行符。以下是修改过的版本，它将每个print语句覆盖标签改为追加到标签中。

    class StdoutRedirector(IORedirector):
        def write(self,str):
           self.TEXT_INFO.config(text=self.TEXT_INFO.cget('text') + str)

- Jesse Harris

---

你太棒了！这个程序完美地运行了！谢谢你的帮助，我不知道print语句总是在输出后发送一个换行符到标准输出流，现在我知道了;-)（我不能投票因为我的声望还不到15分，但是一旦我有了，我会给你投票的；） - user1422695

Answer 2

我创建了一个类，将标准输出的写入调用复制到一个tkinter小部件中，无论是Label还是Text。在Python3.3.1/WindowsXp上为我工作。

import sys

class StdoutToWidget:
    '''
    Retrieves sys.stdout and show write calls also in a tkinter
    widget. It accepts widgets which have a "text" config and defines
    their width and height in characters. It also accepts Text widgets.
    Use stop() to stop retrieving.

    You can manage output height by using the keyword argument. By default
    the class tries to get widget\'s height configuration and use that. If
    that fails it sets self.height to None which you can also do manually.
    In this case the output will not be trimmed. However if you do not
    manage your widget, it can grow vertically hard by getting more and
    more inputs.
    '''

    # Inspired by Jesse Harris and Stathis
    # https://dev59.com/mGTWa4cB1Zd3GeqPDnzo#10846997
    # https://dev59.com/Ym7Xa4cB1Zd3GeqPlxj1

    # TODO: horizontal wrapping
    #       make it a widget decorator (if possible)
    #       height management for Text widget mode

    def __init__(self, widget, height='default', width='default'):
        self._content = []
        self.defstdout = sys.stdout
        self.widget = widget

        if height == 'default':
            try:
                self.height = widget.cget('height')
            except:
                self.height = None
        else:
            self.height = height
        if width == 'default':
            try:
                self.width = widget.cget('width')
            except:
                self.width = None
        else:
            self.width = width   

    def flush(self):
        '''
        Frame sys.stdout's flush method.
        '''
        self.defstdout.flush()

    def write(self, string, end=None):
        '''
        Frame sys.stdout's write method. This method puts the input
        strings to the widget.
        '''

        if string is not None:
            self.defstdout.write(string)
            try:
                last_line_last_char = self._content[-1][-1]
            except IndexError:
                last_line_last_char = '\n'
            else:
                if last_line_last_char == '\n':
                    self._content[-1] = self._content[-1][:-1]

            if last_line_last_char != '\n' and string.startswith('\r'):
                self._content[-1] = string[1:]
            elif last_line_last_char != '\n':
                self._content[-1] += string
            elif last_line_last_char == '\n' and string.startswith('\r'):
                self._content.append(string[1:])
            else:
                self._content.append(string)

        if hasattr(self.widget, 'insert') and hasattr(self.widget, 'see'):
            self._write_to_textwidget()
        else:
            self._write_to_regularwidget(end)

    def _write_to_regularwidget(self, end):
        if self.height is None:
            self.widget.config(text='\n'.join(self.content))
        else:
            if not end:
                content = '\n'.join(self.content[-self.height:])
            else:
                content = '\n'.join(self.content[-self.height+end:end])
            self.widget.config(text=content)

    def _write_to_textwidget(self):
        self.widget.insert('end', '\n'.join(self.content))
        self.widget.see('end')        

    def start(self):
        '''
        Starts retrieving.
        '''
        sys.stdout = self

    def stop(self):
        '''
        Stops retrieving.
        '''
        sys.stdout = self.defstdout

    @property
    def content(self):
        c = []
        for li in self._content:
            c.extend(li.split('\n'))

        if not self.width:
            return c
        else:
            result = []
            for li in c:
                while len(li) > self.width:
                    result.append(li[:self.width])
                    li = li[self.width:]
                result.append(li)
            return result

    @content.setter
    def content(self, string):
        self._content = string.split('\n')

    @property
    def errors(self):
        return self.defstdout.errors

    @property
    def encoding(self):
        return self.defstdout.encoding

编辑1：我收到了一次负评，所以这里是更新后的版本。我在Label widget中使用它，并且print()函数可以在我的widget中平稳运行。此外，如果我将None传递给write调用，并将-1作为结束参数，那么它不会显示最后一行（要小心索引）。我之所以使用它，是因为我将一个滑块附加到该widget上。我很快就会发布演示。

- SzieberthAdam