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Selecting data frame rows based on partial string match in a column
...emember that subsetting approaches for data.frames and data.tables are not identical):
library(data.table)
mtcars[rownames(mtcars) %like% "Merc", ]
iris[iris$Species %like% "osa", ]
If that is what you had, then perhaps you had just mixed up row and column positions for subsetting data.
If you...
How to return dictionary keys as a list in Python?
... to doing list(iterable) and its behaviour was initially documented in the Calls section of the Python Reference manual. With PEP 448 the restriction on where *iterable could appear was loosened allowing it to also be placed in list, set and tuple literals, the reference manual on Expression lists w...
What does it mean if a Python object is “subscriptable” or not?
...
It basically means that the object implements the __getitem__() method. In other words, it describes objects that are "containers", meaning they contain other objects. This includes strings, lists, tuples, and dictionaries.
...
Does deleting a branch in git remove it from the history?
...nd tags (by convention) live in separate 'folders' of the repository alongside the special 'trunk'.
If the branch was merged into another branch before it was deleted then all of the commits will still be reachable from the other branch when the first branch is deleted. They remain exactly as they ...
How to get a random number in Ruby
...2 + rand(6) + rand(6).
Finally, if you just need a random float, just call rand with no arguments.
As Marc-André Lafortune mentions in his answer below (go upvote it), Ruby 1.9.2 has its own Random class (that Marc-André himself helped to debug, hence the 1.9.2 target for that feature).
...
How to implement a queue using two stacks?
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Keep 2 stacks, let's call them inbox and outbox.
Enqueue:
Push the new element onto inbox
Dequeue:
If outbox is empty, refill it by popping each element from inbox and pushing it onto outbox
Pop and return the top element from outbox
Usi...
mkdir -p functionality in Python [duplicate]
...shell from within Python. I am looking for a solution other than a system call. I am sure the code is less than 20 lines, and I am wondering if someone has already written it?
...
How do you pass a function as a parameter in C?
...the proper type:
void print ( int x ) {
printf("%d\n", x);
}
Function Call
When calling a function with a function parameter, the value passed must be a pointer to a function. Use the function's name (without parentheses) for this:
func(print);
would call func, passing the print function to...
Python argparse: How to insert newline in the help text?
... " d = delta\n"
" e = epsilon")
parser.parse_args()
Any other calls to .add_argument() where the help does not start with R| will be wrapped as normal.
This is part of my improvements on argparse. The full SmartFormatter also supports adding
the defaults to all options, and raw input o...
PDO support for multiple queries (PDO_MYSQL, PDO_MYSQLND)
...PDO::ATTR_EMULATE_PREPARES is set to 1 (default). Alternatively you can avoid using prepared statements and use $pdo->exec directly.
Using exec
$db = new PDO("mysql:host=localhost;dbname=test", 'root', '');
// works regardless of statements emulation
$db->setAttribute(PDO::ATTR_EMULATE_PREPA...