blocks|key|2014430|text|将第6行更改为|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2014431|Hex=int(input('Enter+a+hex+number:+'),+16)|code-block|syntax|javascript|2014432|此行将成功解析任何十六进制输入(例如，'0x123f')，并将在无效输入(例如，‘ValueError’)上抛出ValueError。|2014433|ETA:根据你的评论，以下是你需要的：|2014434|user_input+=+input('Enter+a+hex+number:+')
try:
++++hexval+=+int(user_input,+16)
++++print+'That+is+a+valid+hex+value.'
except:
++++print+'That+is+an+invalid+hex+value.'|2014435|ETA:如果你真的需要一个Check函数，这个结构将是最好的方法：|offset|length|style|CODE|2014436|import+re

def+Check(s):
++++"""Check+if+a+string+is+a+valid+hexadecimal+number"""
++++#+code+for+checking+if+it+is+a+valid+hex+number+here

user_input+=+raw_input("Enter+a+hex+number:+")
if+Check(user_input):
++++print+'That+is+a+valid+hex+value.'
else:
++++print+'That+is+an+invalid+hex+value.'|2014437|因为这是一个家庭作业问题，所以我不打算完成答案--只要知道如果字符串是有效的十六进制语句，Check函数必须返回True，否则返回False。|2014438|在每个人的答案中都有很多关于如何做到这一点的想法，你确实可以像我上面做的那样使用try/except语句。最好的方法之一是使用regular+expressions，这是一种非常强大的解析字符串的方法。|2014439|entityMap|0|LINK|mutability|MUTABLE|url|http://www.regular-expressions.info/^0|0|0|0|0|0|D|5|0|0|19|5|0|1R|J|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|17|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|18|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|19|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|1A|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|1B|8|@$O|1C|P|1D|Q|R]]|9|@]|A|$]]|$1|S|3|T|5|D|7|1E|8|@]|9|@]|A|$E|F]]|$1|U|3|V|5|6|7|1F|8|@$O|1G|P|1H|Q|R]]|9|@]|A|$]]|$1|W|3|X|5|6|7|1I|8|@]|9|@$O|1J|P|1K|1|1L]]|A|$]]|$1|Y|3|-4|5|6|7|1M|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15]]]]

Change line 6 to

<pre><code>Hex=int(input('Enter a hex number: '), 16)
</code></pre>

This line would successfully parse any hexadecimal input (for example, '0x123f') and would throw a ValueError on an invalid input (such as 'hello').

ETA: Based on your comments, the following is all you need:

<pre><code>user_input = input('Enter a hex number: ')
try:
 hexval = int(user_input, 16)
 print 'That is a valid hex value.'
except:
 print 'That is an invalid hex value.'
</code></pre>

ETA: If you really have to have a <code>Check</code> function, this structure would be the best way to do it:

<pre><code>import re

def Check(s):
 """Check if a string is a valid hexadecimal number"""
 # code for checking if it is a valid hex number here

user_input = raw_input("Enter a hex number: ")
if Check(user_input):
 print 'That is a valid hex value.'
else:
 print 'That is an invalid hex value.'
</code></pre>

Since this is a homework question I'm not going to finish the answer- just know that the <code>Check</code> function has to return True if the string is a valid hex statement or False if the string is not.

There are many ideas among everyone's answers of how to do it, and you could indeed use a try/except statement like I do above. One of the best ways to do it would be to use <a href="http://www.regular-expressions.info/" rel="nofollow">regular expressions</a>, which are a very powerful way to parse strings.

blocks|key|2784364|text|研究regex库。或者显式转换为int，然后捕获任何错误并相应地处理它们。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2784365|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Investigate the regex library. Or do explicit cast to int then catch any errors and process them accordingly.

blocks|key|2784377|text|十六进制字符串的唯一有效值是0-9,+A-F。应该可以将这些值存储在列表/数组中，然后执行简单的contains调用。大致是这样的：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2784378|++for+char+in+userInput:++
++++++if+not+char+in+validTokens:++
++++++++++print+'invalid+hex+value'|code-block|syntax|javascript|2784379|entityMap^0|E|8|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

The only valid values for hex strings are <code>0-9, A-F</code> . It should be possible to store these values in a list / array and then do a simple contains call. Something along the lines of this: 

<pre><code> for char in userInput: 
 if not char in validTokens: 
 print 'invalid hex value'
</code></pre>

blocks|key|4897145|text|这是一个很好的Python方法，可以用来检查输入的十六进制数字是否有效。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4897146|def+Check():
++++while+not+Valid:
++++++++try:
++++++++++++Hex=int(raw_input('Enter+a+hex+number:+'),+16)
++++++++++++print('That+is+valid.')
++++++++++++return+True
++++++++except+ValueError:
++++++++++++print('That+is+an+invalid+entry.')
++++++++++++return+False|code-block|syntax|javascript|4897147|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Here is a nice, Python way to check your input for a valid hex number.

<pre><code>def Check():
 while not Valid:
 try:
 Hex=int(raw_input('Enter a hex number: '), 16)
 print('That is valid.')
 return True
 except ValueError:
 print('That is an invalid entry.')
 return False
</code></pre>

blocks|key|2784419|text|我从Python哲学的角度回答这个问题，因为您已经收到了很好的答案，其中一些涉及到try:+..+except。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2784420|关于使用异常处理try:+..+except的Python化的东西是，Python程序员似乎被鼓励使用它的方式，至少对我来说，与其他语言中的异常处理不同。|2784421|在Python中，建议您在try+..的构造中显式使用raise或更隐式地使用raise来引发异常。除了。|2784422|不久前，当我提出一个关于如何处理.csv文件中的空整数值的问题时，有人鼓励我继续在try：.中对Python整型变量进行赋值。除了，而不是先测试以确定值是否为空。|2784423|答案继续说，不要费心测试然后采取行动，使用异常处理，因为它更具Pythonic风格。使用try：..但似乎也消耗了更少的指令。|2784424|这种态度使我编写了更多的异常处理，而不是使用try：..除了只在发生不好的事情时保留。|2784425|entityMap^0|15|E|0|8|E|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|X|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|Y|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|Z|8|@]|D|@]|E|$]]|$1|N|3|O|5|6|7|10|8|@]|D|@]|E|$]]|$1|P|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|Q|$]]

I am answering this question from a Python philosophy point of view, because you have already received good answers, some of them involving <code>try: .. except</code>.

The Pythonic thing about using exception handling <code>try: .. except</code> is the way Python programmers seem to be encouraged to use it is, at least for me, a departure from exception handling in other languages. 

In Python, you are encouraged to raise an exception, either explicitly using raise or more implicitly within the construct of try .. except. 

When I posed a question a while back about how to deal with null integer values in a .csv file, I was encouraged to go ahead with the assignment to the Python integer variable within try: .. except, instead of testing first to test to see if the value was null.

The answer went on to say don't bother to test and then take action, use exception handling, because it is more Pythonic. Using try: .. except also appeared to consume fewer instructions. 

That attitude got me to write more exception handling than I would have thinking using try: .. except was reserved only for when bad things happen.

blocks|key|2784444|text|表达式string.translate(x，None，"0123456789abcdefABCDEF")+==+'‘为True仅当x包含有效的十六进制字符，或者x为空字符串。(您需要“导入字符串”。)显然，这可用于验证字符串是否只包含任何给定集合中的字符(或为空)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2784445|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

The expression
 string.translate(x, None, "0123456789abcdefABCDEF") == ''
is True iff x contains valid hexadecimal characters, or x is the null string.(You need to "import string".)
 Obviously this can be used to validate that a string contains only characters from any given set (or is null).

<pre><code>#Hex Check
def Check():
 while False:
 for char in UserInput:
 if char not in Valid:
 print ('That is an invalid hex value.')
 print('That is a valid hex value.')
 return Check

UserInput=input('Enter a hex number: ')
Valid='1''2''3''4''5''6''7''8''9''10''A''B''C''D''E''F'
</code></pre>

EDIT: I've tried this. When I enter a hex value e.g. B2 no message comes up.

How can I determine if user input is a valid hexadecimal number? 

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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#Hex Checkdef Check():    while False:        for char in UserInput:            if char not in Valid:                print ('That is an invalid hex value.')    ...

问如何确定用户输入是否为有效的十六进制数？
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问如何确定用户输入是否为有效的十六进制数？EN