问题:输出到同一行覆盖先前的输出?

我正在写一个FTP下载器。代码的一部分是这样的:

ftp.retrbinary("RETR " + file_name, process)

我正在调用函数进程来处理回调:

def process(data):
    print os.path.getsize(file_name)/1024, 'KB / ', size, 'KB downloaded!'
    file.write(data)

输出是这样的:

1784  KB / KB 1829 downloaded!
1788  KB / KB 1829 downloaded!
etc...   

但我希望它打印此行,下次重新打印/刷新它,因此它只会显示一次,我会看到下载进度。

如何做呢?

I am writing an FTP downloader. Part of to the code is something like this:

ftp.retrbinary("RETR " + file_name, process)

I am calling function process to handle the callback:

def process(data):
    print os.path.getsize(file_name)/1024, 'KB / ', size, 'KB downloaded!'
    file.write(data)

and output is something like this:

1784  KB / KB 1829 downloaded!
1788  KB / KB 1829 downloaded!
etc...   

but I want it to print this line and next time reprint/refresh it so it will only show it once and I will see progress of that download.

How can it be done?


回答 0

这是Python 3.x的代码:

print(os.path.getsize(file_name)/1024+'KB / '+size+' KB downloaded!', end='\r')

end=关键字是什么做的工作在这里-在默认情况下,print()在一个换行符(结束\n)字符,但可以使用不同的字符串替换。在这种情况下,用回车符结束该行,而是将光标返回到当前行的开头。因此,无需sys为此类简单用法导入模块。print()实际上有许多关键字参数可以用来大大简化代码。

要在Python 2.6+上使用相同的代码,请将以下行放在文件顶部:

from __future__ import print_function

Here’s code for Python 3.x:

print(os.path.getsize(file_name)/1024+'KB / '+size+' KB downloaded!', end='\r')

The end= keyword is what does the work here — by default, print() ends in a newline (\n) character, but this can be replaced with a different string. In this case, ending the line with a carriage return instead returns the cursor to the start of the current line. Thus, there’s no need to import the sys module for this sort of simple usage. print() actually has a number of keyword arguments which can be used to greatly simplify code.

To use the same code on Python 2.6+, put the following line at the top of the file:

from __future__ import print_function

回答 1

如果您只想更改一行,请使用\r\r表示回车。它的作用仅仅是将插入号放回当前行的开头。它不会删除任何内容。同样,\b可用于向后退一个字符。(某些终端可能不支持所有这些功能)

import sys

def process(data):
    size_str = os.path.getsize(file_name)/1024, 'KB / ', size, 'KB downloaded!'
    sys.stdout.write('%s\r' % size_str)
    sys.stdout.flush()
    file.write(data)

If all you want to do is change a single line, use \r. \r means carriage return. It’s effect is solely to put the caret back at the start of the current line. It does not erase anything. Similarly, \b can be used to go one character backward. (some terminals may not support all those features)

import sys

def process(data):
    size_str = os.path.getsize(file_name)/1024, 'KB / ', size, 'KB downloaded!'
    sys.stdout.write('%s\r' % size_str)
    sys.stdout.flush()
    file.write(data)

回答 2

看一下curses模块文档curses模块HOWTO

真正的基本例子:

import time
import curses

stdscr = curses.initscr()

stdscr.addstr(0, 0, "Hello")
stdscr.refresh()

time.sleep(1)

stdscr.addstr(0, 0, "World! (with curses)")
stdscr.refresh()

Have a look at the curses module documentation and the curses module HOWTO.

Really basic example:

import time
import curses

stdscr = curses.initscr()

stdscr.addstr(0, 0, "Hello")
stdscr.refresh()

time.sleep(1)

stdscr.addstr(0, 0, "World! (with curses)")
stdscr.refresh()

回答 3

这是我的小类,可以重印文本块。它会正确清除先前的文本,因此您可以用较短的新文本覆盖旧文本而不会造成混乱。

import re, sys

class Reprinter:
    def __init__(self):
        self.text = ''

    def moveup(self, lines):
        for _ in range(lines):
            sys.stdout.write("\x1b[A")

    def reprint(self, text):
        # Clear previous text by overwritig non-spaces with spaces
        self.moveup(self.text.count("\n"))
        sys.stdout.write(re.sub(r"[^\s]", " ", self.text))

        # Print new text
        lines = min(self.text.count("\n"), text.count("\n"))
        self.moveup(lines)
        sys.stdout.write(text)
        self.text = text

reprinter = Reprinter()

reprinter.reprint("Foobar\nBazbar")
reprinter.reprint("Foo\nbar")

Here’s my little class that can reprint blocks of text. It properly clears the previous text so you can overwrite your old text with shorter new text without creating a mess.

import re, sys

class Reprinter:
    def __init__(self):
        self.text = ''

    def moveup(self, lines):
        for _ in range(lines):
            sys.stdout.write("\x1b[A")

    def reprint(self, text):
        # Clear previous text by overwritig non-spaces with spaces
        self.moveup(self.text.count("\n"))
        sys.stdout.write(re.sub(r"[^\s]", " ", self.text))

        # Print new text
        lines = min(self.text.count("\n"), text.count("\n"))
        self.moveup(lines)
        sys.stdout.write(text)
        self.text = text

reprinter = Reprinter()

reprinter.reprint("Foobar\nBazbar")
reprinter.reprint("Foo\nbar")

回答 4

我发现对于python 2.7中的一个简单的print语句,只需将逗号放在your的末尾'\r'

print os.path.getsize(file_name)/1024, 'KB / ', size, 'KB downloaded!\r',

这比其他非python 3解决方案要短,但也更难以维护。

I found that for a simple print statement in python 2.7, just put a comma at the end after your '\r'.

print os.path.getsize(file_name)/1024, 'KB / ', size, 'KB downloaded!\r',

This is shorter than other non-python 3 solutions, but also more difficult to maintain.


回答 5

您只需在字符串末尾添加“ \ r”,然后在打印功能末尾添加逗号。例如:

print(os.path.getsize(file_name)/1024+'KB / '+size+' KB downloaded!\r'),

You can just add ‘\r’ at the end of the string plus a comma at the end of print function. For example:

print(os.path.getsize(file_name)/1024+'KB / '+size+' KB downloaded!\r'),

回答 6

我正在使用spyder 3.3.1-Windows 7-python 3.6,尽管可能不需要刷新。基于此帖子-https: //github.com/spyder-ide/spyder/issues/3437

   #works in spyder ipython console - \r at start of string , end=""
import time
import sys
    for i in range(20):
        time.sleep(0.5)
        print(f"\rnumber{i}",end="")
        sys.stdout.flush()

I am using spyder 3.3.1 – windows 7 – python 3.6 although flush may not be needed. based on this posting – https://github.com/spyder-ide/spyder/issues/3437

   #works in spyder ipython console - \r at start of string , end=""
import time
import sys
    for i in range(20):
        time.sleep(0.5)
        print(f"\rnumber{i}",end="")
        sys.stdout.flush()

回答 7

要超越python中的前一行,您需要做的就是在打印函数中添加end =’\ r’,请测试以下示例:

import time
for j in range(1,5):
   print('waiting : '+j, end='\r')
   time.sleep(1)

to overwiting the previous line in python all wath you need is to add end=’\r’ to the print function, test this example:

import time
for j in range(1,5):
   print('waiting : '+j, end='\r')
   time.sleep(1)

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