如何将print语句重定向到Tkinter文本小部件

时间:2012-09-10 12:30:50

标签: python tkinter

我有一个Python程序,它执行一组操作并在STDOUT上打印响应。现在我正在编写一个GUI,它将调用已经存在的代码,我想在GUI中打印相同的内容而不是STDOUT。我将使用Text小部件来实现此目的。我不想修改执行任务的现有代码(此代码也被其他程序使用)。

有人可以指出我如何使用现有的任务定义并使用其STDOUT结果并将其插入文本小部件中吗?在主GUI程序中,我想调用此任务定义并将其结果打印到STDOUT。有没有办法使用这些信息?

5 个答案:

答案 0 :(得分:15)

您可以通过将sys.stdout替换为您自己的写入文本小部件的类文件对象来解决此问题。

例如:

import Tkinter as tk
import sys

class ExampleApp(tk.Tk):
    def __init__(self):
        tk.Tk.__init__(self)
        toolbar = tk.Frame(self)
        toolbar.pack(side="top", fill="x")
        b1 = tk.Button(self, text="print to stdout", command=self.print_stdout)
        b2 = tk.Button(self, text="print to stderr", command=self.print_stderr)
        b1.pack(in_=toolbar, side="left")
        b2.pack(in_=toolbar, side="left")
        self.text = tk.Text(self, wrap="word")
        self.text.pack(side="top", fill="both", expand=True)
        self.text.tag_configure("stderr", foreground="#b22222")

        sys.stdout = TextRedirector(self.text, "stdout")
        sys.stderr = TextRedirector(self.text, "stderr")

    def print_stdout(self):
        '''Illustrate that using 'print' writes to stdout'''
        print "this is stdout"

    def print_stderr(self):
        '''Illustrate that we can write directly to stderr'''
        sys.stderr.write("this is stderr\n")

class TextRedirector(object):
    def __init__(self, widget, tag="stdout"):
        self.widget = widget
        self.tag = tag

    def write(self, str):
        self.widget.configure(state="normal")
        self.widget.insert("end", str, (self.tag,))
        self.widget.configure(state="disabled")

app = ExampleApp()
app.mainloop()

答案 1 :(得分:3)

在python中,无论何时调用print('examplestring'),都要间接调用sys.stdout.write('examplestring') :

from tkinter import *
root=Tk()
textbox=Text(root)
textbox.pack()
button1=Button(root, text='output', command=lambda : print('printing to GUI'))
button1.pack()

方法1:在GUI上打印

def redirector(inputStr):
    textbox.insert(INSERT, inputStr)

sys.stdout.write = redirector #whenever sys.stdout.write is called, redirector is called.

root.mainloop()

事实上,我们正在调用print - (callsfor) - > sys.stdout.write - (callsfor) - >重定向器

方法2:编写装饰器 - 在CLI和GUI上打印

def decorator(func):
    def inner(inputStr):
        try:
            textbox.insert(INSERT, inputStr)
            return func(inputStr)
        except:
            return func(inputStr)
    return inner

sys.stdout.write=decorator(sys.stdout.write)
#print=decorator(print)  #you can actually write this but not recommended

root.mainloop()

装饰器做的是它实际上将func sys.stdout.write分配给func inner

sys.stdout.write=inner

和func inner在回调实际的sys.stdout.write之前添加了一行额外的代码

这样可以更新旧的func sys.stdout.write以获得新功能。 您会注意到我使用了try-except,如果打印到文本框时出现任何错误,我至少会将sys.stdout.write的原始函数保留到CLI

方法3:Bryan Oakley的例子

...
    sys.stdout = TextRedirector(self.text, "stdout")
...
class TextRedirector(object):
    def __init__(self, widget, tag="stdout"):
        self.widget = widget
        self.tag = tag

    def write(self, str):
        self.widget.configure(state="normal")
        self.widget.insert("end", str, (self.tag,))
        self.widget.configure(state="disabled")

他所做的是他使用Method .write(str)将sys.stdout分配给Class TextRedirector

所以打电话 print('string')-calls for-> sys.stdout.write('string')-callsfor-> TextRedirector.write('string')

答案 2 :(得分:1)

您可以使用subprocess.Popen调用CLI程序,获取它生成的标准输出,并在文本小部件中显示它。

(未经测试)的某些内容:

import subprocess

with subprocess.Popen(your_CLI_program, stdout=subprocess.PIPE) as cli
    line = cli.stdout.readline()

    #process the output of your_CLI_program
    print (line)

请注意,这将阻止,直到CLI程序完成执行,冻结GUI。为了解决阻塞问题,您可以将此代码放在threading.Thread中,并在等待线程完成时让GUI更新。

答案 3 :(得分:0)

事实上,我认为这个问题不仅限于tkinter。可以应用任何框架,因为它实际上是在重定向sys.stdout

我创建了一个课程(RedirectStdMsg)。

tl; dr

original = sys.stdout
sys.stdout = everything_you_like
...
sys.stdout = original  # restore

import sys
from typing import TextIO
from typing import Callable
# import tkinter as tk

class RedirectStdMsg:
    __slots__ = ('original', 'output_device',)

    def __init__(self, sys_std: TextIO):
        self.output_device = None
        self.original = sys_std

    def __call__(self, output_device=Callable[[str], None]):
        self.output_device = output_device
        return self

    def __enter__(self):
        if self.output_device is None:
            raise AttributeError('output_device is empty')
        self.start(self.output_device)

    def __exit__(self, exc_type, exc_val, exc_tb):
        if exc_val:
            self.write(str(exc_val))
        self.stop()

    def start(self, output_device):
        self.output_device = output_device
        std_name = self.original.name.translate(str.maketrans({'<': '', '>': ''}))
        exec(f'sys.{std_name} = self')  # just like: ``sys.stderr = self``

    def stop(self):
        std_name = self.original.name.translate(str.maketrans({'<': '', '>': ''}))
        exec(f'sys.{std_name} = self.original')
        self.output_device = None

    def write(self, message: str):
        """ When sys.{stderr, stdout ...}.write is called, it will redirected here"""
        if self.output_device is None:
            self.original.write(message)
            self.original.flush()
            return
        self.output_device(message)

测试

测试tk类

由@Bryan Oakley修改

class ExampleApp(tk.Tk):
    def __init__(self, **options):
        tk.Tk.__init__(self)
        toolbar = tk.Frame(self)
        toolbar.pack(side="top", fill="x")
        b1 = tk.Button(self, text="print to stdout", command=self.print_stdout)
        b2 = tk.Button(self, text="print to stderr", command=self.print_stderr)
        b1.pack(in_=toolbar, side="left")
        b2.pack(in_=toolbar, side="left")
        self.text = tk.Text(self, wrap="word")
        self.text.pack(side="top", fill="both", expand=True)
        self.text.tag_configure("stderr", foreground="#b22222")

        self.re_stdout = options.get('stdout')
        self.re_stderr = options.get('stderr')

        if self.re_stderr or self.re_stderr:
            tk.Button(self, text='Start redirect', command=self.start_redirect).pack(in_=toolbar, side="left")
            tk.Button(self, text='Stop redirect', command=self.stop_redirect).pack(in_=toolbar, side="left")

    def start_redirect(self):
        self.re_stdout.start(TextRedirector(self.text, "stdout").write) if self.re_stdout else ...
        self.re_stderr.start(TextRedirector(self.text, "stderr").write) if self.re_stderr else ...

    def stop_redirect(self):
        self.re_stdout.stop() if self.re_stdout else ...
        self.re_stderr.stop() if self.re_stderr else ...

    @staticmethod
    def print_stdout():
        """Illustrate that using 'print' writes to stdout"""
        print("this is stdout")

    @staticmethod
    def print_stderr():
        """Illustrate that we can write directly to stderr"""
        sys.stderr.write("this is stderr\n")


class TextRedirector(object):
    def __init__(self, widget, tag="stdout"):
        self.widget = widget
        self.tag = tag

    def write(self, msg):
        self.widget.configure(state="normal")
        self.widget.insert("end", msg, (self.tag,))
        self.widget.configure(state="disabled")

测试案例

def test_tk_without_stop_btn():
    app = ExampleApp()
    with RedirectStdMsg(sys.stdout)(TextRedirector(app.text, "stdout").write), \
            RedirectStdMsg(sys.stderr)(TextRedirector(app.text, "stderr").write):
        app.mainloop()


def test_tk_have_stop_btn():
    director_out = RedirectStdMsg(sys.stdout)
    director_err = RedirectStdMsg(sys.stderr)
    app = ExampleApp(stdout=director_out, stderr=director_err)
    app.mainloop()


def test_to_file():

    # stdout test
    with open('temp.stdout.log', 'w') as file_obj:
        with RedirectStdMsg(sys.stdout)(file_obj.write):
            print('stdout to file')
    print('stdout to console')


    # stderr test
    with open('temp.stderr.log', 'w') as file_obj:
        with RedirectStdMsg(sys.stderr)(file_obj.write):
            sys.stderr.write('stderr to file')
    sys.stderr.write('stderr to console')

    # another way
    cs_stdout = RedirectStdMsg(sys.stdout)
    cs_stdout.start(open('temp.stdout.log', 'a').write)
    print('stdout to file 2')
    ...
    cs_stdout.stop()
    print('stdout to console 2')


if __name__ == '__main__':
    test_to_file()
    test_tk_without_stop_btn()
    test_tk_have_stop_btn()

这是test_tk_have_stop_btn(): enter image description here

答案 4 :(得分:-1)

通常打印到stdout的函数应该将文本放入文本小部件中。