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When do we need curly braces around shell variables?
...xpand the variable identified by foobar.
Curly braces are also unconditionally required when:
expanding array elements, as in ${array[42]}
using parameter expansion operations, as in ${filename%.*} (remove extension)
expanding positional parameters beyond 9: "$8 $9 ${10} ${11}"
Doing this every...
“Private” (implementation) class in Python
I am coding a small Python module composed of two parts:
7 Answers
7
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How to create a trie in Python
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Unwind is essentially correct that there are many different ways to implement a trie; and for a large, scalable trie, nested dictionaries might become cumbersome -- or at least space inefficient. But since you're just getting started, I think...
Commenting in a Bash script inside a multiline command
... works fine. So too does cat file1 && # comment<newline>echo foo. So comments can be included after | or && or ||, but not after `\` or in the middle of a command.
– dubiousjim
Jan 12 '13 at 22:53
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configure Git to accept a particular self-signed server certificate for a particular https remote
...ct repos.sample.com:443
Catch the output into a file cert.pem and delete all but part between (and including) -BEGIN CERTIFICATE- and -END CERTIFICATE-
Content of resulting file ~/git-certs/cert.pem may look like this:
-----BEGIN CERTIFICATE-----
MIIDnzCCAocCBE/xnXAwDQYJKoZIhvcNAQEFBQAwgZMxCzAJB...
How do I format a string using a dictionary in python-3.x?
...3). In many languages, it is known as splat operator. In JavaScript, it's called spread operator. In python, there is no particular name given to this operator.
– abhisekp
Apr 15 '17 at 12:01
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What does the exclamation mark mean in a Haskell declaration?
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It's a strictness declaration. Basically, it means that it must be evaluated to what's called "weak head normal form" when the data structure value is created. Let's look at an example, so that we can see just what this means:
data Foo = Foo Int Int !Int !(May...
理解Python的 with 语句 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...he lines of: 如果不用with语句，代码如下：
file = open("/tmp/foo.txt")
data = file.read()
file.close()
There are two annoying things here. First, you end up forgetting to close the file handler. The second is how to handle exceptions that may occur once the file handler has been obt...
A python class that acts like dict
...er) instead of simply delegating to the instance's __dict__ - which essentially means you're creating two dicts for every instance.
– Aaron Hall♦
Jan 8 '17 at 0:39
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ASP.NET MVC: Custom Validation by DataAnnotation
...ationContext.ObjectInstance, null)).OfType<string>();
var totalLength = values.Sum(x => x.Length) + Convert.ToString(value).Length;
if (totalLength < this.MinLength)
{
return new ValidationResult(this.FormatErrorMessage(validationContext.DisplayName));...