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Selecting multiple columns in a pandas dataframe
...).
df1 = df[['a', 'b']]
Alternatively, if it matters to index them numerically and not by their name (say your code should automatically do this without knowing the names of the first two columns) then you can do this instead:
df1 = df.iloc[:, 0:2] # Remember that Python does not slice inclusive of...
Get keys from HashMap in Java
...HashMap contains more than one key. You can use keySet() to get the set of all keys.
team1.put("foo", 1);
team1.put("bar", 2);
will store 1 with key "foo" and 2 with key "bar". To iterate over all the keys:
for ( String key : team1.keySet() ) {
System.out.println( key );
}
will print "foo"...
What is the purpose of the single underscore “_” variable in Python?
...cate that part
of a function result is being deliberately ignored (Conceptually, it is being discarded.), as in code like:
label, has_label, _ = text.partition(':').
As part of a function definition (using either def or lambda), where
the signature is fixed (e.g. by a callback or parent class API), ...
Should a return statement be inside or outside a lock?
...d then returning it (outside the lock), then I'd say that a simple "return foo" inside the lock is a lot simpler.
To show the difference in IL, lets code:
static class Program
{
static void Main() { }
static readonly object sync = new object();
static int GetValue() { return 5; }
...
How do you add Boost libraries in CMakeLists.txt?
... it can also help to add this to your cmake file: ADD_DEFINITIONS( -DBOOST_ALL_NO_LIB ) otherwise you may run into stackoverflow.com/questions/28887680/…
– Stéphane
Jul 22 '15 at 16:08
...
How do I append one string to another in Python?
...ugh memory to resize the string, the original
string object at *pv is deallocated, *pv is set to NULL, an "out of
memory" exception is set, and -1 is returned. Else (on success) 0 is
returned, and the value in *pv may or may not be the same as on input.
As always, an extra byte is alloc...
Explain the encapsulated anonymous function syntax
...ression:
(function foo() {
alert(2 + 2);
}());
The Parentheses (formally called the Grouping Operator) can surround only expressions, and a function expression is evaluated.
The two grammar productions can be ambiguous, and they can look exactly the same, for example:
function foo () {} // ...
dynamic_cast and static_cast in C++
...
Here's a rundown on static_cast<> and dynamic_cast<> specifically as they pertain to pointers. This is just a 101-level rundown, it does not cover all the intricacies.
static_cast< Type* >(ptr)
This takes the pointer in ptr and tries to safely cast it to a pointer of type Type...
How to get the concrete class name as a string? [duplicate]
... Is there a way to get it with the import path? For example, str(type(foo)) == "<class 'never.gonna.give.youup'>" but type(foo).__name__ == "youup". How do I get never.gonna.give.youup?
– Martin Thoma
Apr 29 '19 at 8:00
...
How to check that an element is in a std::set?
... Note that using count() instead of find() is never better but potentially worse. This is because find() will return after the first match, count() will always iterate over all elements.
– Frerich Raabe
Nov 9 '09 at 15:50
...