太多的价值无法解包 [英] Too many values to unpack

问题描述

我正在努力学习python， 在第15章中，我想使用import argv分配变量和原始输入以获得 用户输入.脚本是:

I'm reading learn python the hard way, and on chapter 15 I'm suppose to use import argv to assign variables and raw input to gain user input. The script is:

from sys import argv 

script, filename, = argv

txt = open(filename)

print " Here's your file %r :" % filename
print  txt.read()

print " I'll also ask you to type it again: "

file_again = raw_input ("> ")

txt_again = open (file_again)

print txt_again.read ()

运行此脚本后，出现错误，无法解包的值太多.

After running this script I get the error, too many values to unpack.

文件"ex15.py"，第3行，在 脚本，文件名= argv
值错误:无法解包的值太多

File "ex15.py", line 3, in script , filename = argv
Value error: too many values to unpack

推荐答案

只是几个指针...

from sys import argv  

script, filename, = argv 

在这里，您要导入argv以访问命令行参数，然后期望它包含2个参数-脚本(arg 0)和要打印的文件名(arg1).尽管结尾的逗号在语法上不是不正确的，但这不是必需的，并且看起来有点奇怪.我通常将argv留在sys内，而不是将其拉入当前名称空间中，但这只是一个趣味问题-并没有真正的区别.我可能还会抛出一些错误处理:

Here you're importing argv to access command line parameters, and then expecting it to contain 2 arguments - script (arg 0) and filename to print (arg1). Although the trailing comma isn't syntatically incorrect, it's not required and just looks a bit odd. I nomally leave argv inside sys instead of pulling it into the current namespace, but that's a matter of taste - it doesn't make a real difference. I would probably throw in a bit of error handling as well:

import sys

try:
    script, filename = sys.argv
except ValueError as e:
    raise SystemExit('must supply single filename as argument')

---

txt = (filename) 

print " Here's your file %r :" % filename 
print  txt.read() 

txt = (name)在这里所做的所有事情都是使txt具有filename的值.我相信您想将txt设为文件对象，以便您可以从其中.read():

All that txt = (name) is doing here is making txt have the value of filename. I believe you want to be making txt a file object, so that you can .read() from it:

txt = open(filename)
print "Here's the file contents of:", filename
print txt.read()

---

print " I'll also ask you to type it again: "     
file_again = raw_input ("> ")     
txt_again = open (file_again)      
print txt.again.read ()

您在这里有open()，但是txt.again.read()应该是txt_again.read()，否则您会得到AttributeError-因此只需更改它就可以了.

You've got the open() here, but txt.again.read() should be txt_again.read() else you'll get an AttributeError - so just change that and it's fine.

或者，文件对象支持查找，因此您可以使用以下方法来rewind文件(由于您已经读完文件，因此不再需要读取内容了).

Alternatively, file objects supporting seeking, so you could just rewind the file (as you've read the file to the end, there's nothing left to read anymore), by using:

txt.seek(0)
print txt.read()

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