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Parse a .py file, read the AST, modify it, then write back the modified source code

...asy, without writing new .py files! If you expand your question to let us know what you actually want to accomplish, new .py files will probably not be involved in the answer at all; I have seen hundreds of Python projects doing hundreds of real-world things, and not a single one of them needed to e...
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Why do we need virtual functions in C++?

...eneric food, cats eat rats, all without virtual. Let's change it a little now so that eat() is called via an intermediate function (a trivial function just for this example): // This can go at the top of the main.cpp file void func(Animal *xyz) { xyz->eat(); } Now our main function is: Anima...
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Re-raise exception with a different type and message, preserving existing information

...ture, the __cause__ attribute is set. The built-in exception handler also knows how to report the exception's “cause” and “context” along with the traceback. In Python 2, it appears this use case has no good answer (as described by Ian Bicking and Ned Batchelder). Bummer. ...
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How to get the original value of an attribute in Rails

...flow.com/a/50973808/9359123 Appending _was is deprecated in rails 5.1, now you should append _before_last_save Something like: before_save object do_something_with object.name_before_last_save end Will return the name value before your last save at database (works for save and create) The...
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Installing Java on OS X 10.9 (Mavericks)

...ary/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home" java -version now gives you java version "1.7.0_45" That's the cleanest way I found to install the latest JRE. You can add the export JAVA_HOME line in your .bashrc to have java permanently in your Terminal: echo export JAVA_HOME=\"/Li...
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is node.js' console.log asynchronous?

... Starting with Node 0.6 this post is obsolete, since stdout is synchronous now. Well let's see what console.log actually does. First of all it's part of the console module: exports.log = function() { process.stdout.write(format.apply(this, arguments) + '\n'); }; So it simply does some formatt...
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How do I print the elements of a C++ vector in GDB?

...db wiki page particularly readable, maybe because it's "slightly" outdated now? For instance, I had the impression that the suggested content of the $HOME/.gdbinit was necessary. At the moment I end up with no such file at all and gdb correctly showing the content of std::vector. However, since duri...
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How can I do a line break (line continuation) in Python?

...ly PEP-8 has changed since these comments were added, as it's fairly clear now that parentheses should be added to wrap long lines: "Long lines can be broken over multiple lines by wrapping expressions in parentheses." – Daniel Feb 8 '12 at 9:04 ...
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Does Swift support reflection?

...intln("Type: \(type)") //Unfortunately this prints only "Type: Metatype" Now assuming TestObject extends NSObject var clazz: NSObject.Type = TestObject.self var instance : NSObject = clazz() if let testObject = instance as? TestObject { println("yes!") //prints "yes!" } Currently, there is...
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How to configure Git post commit hook

...f a new commit: With the latest Git plugin 1.1.14 (that I just release now), you can now do this more >easily by simply executing the following command: curl http://yourserver/jenkins/git/notifyCommit?url=<URL of the Git repository> This will scan all the jobs that’s configured...