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Split data frame string column into multiple columns
...ry(tidyr)
before <- data.frame(
attr = c(1, 30 ,4 ,6 ),
type = c('foo_and_bar', 'foo_and_bar_2')
)
before %>%
separate(type, c("foo", "bar"), "_and_")
## attr foo bar
## 1 1 foo bar
## 2 30 foo bar_2
## 3 4 foo bar
## 4 6 foo bar_2
...
Reference: What is variable scope, which variables are accessible from where and what are “undefined
...cope", or "places from which they are accessible". Just because you wrote $foo = 'bar'; once somewhere in your application doesn't mean you can refer to $foo from everywhere else inside the application. The variable $foo has a certain scope within which it is valid and only code in the same scope ha...
Python Remove last 3 characters of a string
...
Removing any and all whitespace:
foo = ''.join(foo.split())
Removing last three characters:
foo = foo[:-3]
Converting to capital letters:
foo = foo.upper()
All of that code in one line:
foo = ''.join(foo.split())[:-3].upper()
...
When is a C++ destructor called?
...s out of scope,
// but not the object it pointed to. memory leak
if (1) {
Foo *myfoo = new Foo("foo");
}
// pointer is destroyed because it goes out of scope,
// object it points to is deleted. no memory leak
if(1) {
Foo *myfoo = new Foo("foo");
delete myfoo;
}
// no memory leak, object goes o...
Struct Constructor in C++?
...r problems.
If you declare your struct like this:
typedef struct{
int x;
foo(){};
} foo;
You will have problems trying to declare a constructor. This is of course because you haven't actually declared a struct named "foo", you've created an anonymous struct and assigned it the alias "foo". Thi...
Call a “local” function within module.exports from another function in module.exports?
...
Change this.foo() to module.exports.foo()
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Difference between this and self in JavaScript
...nd is not in strict mode, this defaults to window, and therefore
function foo() {
console.log(
window.self === window, // is self window?
window.self === this, // is self this?
this === window // is this window?
);
}
foo(); // true true true
If you're usi...
Is this object-lifetime-extending-closure a C# compiler bug?
...axstack 4
.locals init (
[0] class ConsoleApplication1.Program/Foo/'<>c__DisplayClass1' 'CS$<>8__locals2'
)
IL_0000: newobj instance void ConsoleApplication1.Program/Foo/'<>c__DisplayClass1'::.ctor()
IL_0005: stloc.0
IL_0006: ldloc.0
IL_0007: ldar...
How to convert URL parameters to a JavaScript object?
....replace(/&/g, '","').replace(/=/g,'":"') + '"}')
Example
Parse abc=foo&def=%5Basf%5D&xyz=5 in five steps:
decodeURI: abc=foo&def=[asf]&xyz=5
Escape quotes: same, as there are no quotes
Replace &: abc=foo","def=[asf]","xyz=5
Replace =: abc":"foo","def":"[asf]","xyz":"5
...
Django migration strategy for renaming a model and relationship fields
...0001_initial'),
]
operations = [
migrations.RenameModel('Foo', 'Bar'),
migrations.RenameField('AnotherModel', 'foo', 'bar'),
migrations.RenameField('YetAnotherModel', 'foo', 'bar')
]
You may get some errors if you don't update the names where it's imported e.g...