Tutorial by Examples: en

Due to Node's asynchronous nature, creating or using a directory by first: checking for its existence with fs.stat(), then creating or using it depending of the results of the existence check, can lead to a race condition if the folder is created between the time of the check and the time of ...

In $e:expr, the expr is called the fragment specifier. It tells the parser what kind of tokens the parameter $e is expecting. Rust provides a variety of fragment specifiers to, allowing the input to be very flexible. SpecifierDescriptionExamplesidentIdentifierx, foopathQualified namestd::collection...

extern crate serde; extern crate serde_json; macro_rules! enum_str { ($name:ident { $($variant:ident($str:expr), )* }) => { #[derive(Clone, Copy, Debug, Eq, PartialEq)] pub enum $name { $($variant,)* } impl ::serde::Serialize for $name {...

Say we have an enum DayOfWeek: enum DayOfWeek { SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY; } An enum is compiled with a built-in static valueOf() method which can be used to lookup a constant by its name: String dayName = DayOfWeek.SUNDAY.name(); assert dayName.equal...

It's good practice to document your work for later use, especially if you are coding for a dynamic workload. Good comments should explain why the code is doing something, not what the code is doing. Function Bonus(EmployeeTitle as String) as Double If EmployeeTitle = "Sales" Then ...

Given a sequence of steps we use repeatedly, it's often handy to store it in a function. Pipes allow for saving such functions in a readable format by starting a sequence with a dot as in: . %>% RHS As an example, suppose we have factor dates and want to extract the year: library(magrittr) ...

JSFiddle: https://jsfiddle.net/UnsungHero97/80qod7aL/2/ HTML <div class="box_shadow"></div> CSS .box_shadow { background-color: #1C90F3; width: 200px; height: 100px; margin: 50px; } .box_shadow:after { content: ""; width: 190px; height: ...

The following code will print the arguments to the program, and the code will attempt to convert each argument into a number (to a long): #include <stdlib.h> #include <stdio.h> #include <errno.h> #include <limits.h> int main(int argc, char* argv[]) { for (int ...

:root { --W200: 200px; --W10: 10px; } .Bx2 { width: var(--W200); height: var(--W200); margin: var(--W10); }

Raw direct IO file_get_contents and file_put_contents provide the ability to read/write from/to a file to/from a PHP string in a single call. file_put_contents can also be used with the FILE_APPEND bitmask flag to append to, instead of truncate and overwrite, the file. It can be used along with LO...

child.py import time def main(): print "starting work" time.sleep(1) print "work work work work work" time.sleep(1) print "done working" if __name__ == '__main__': main() parent.py import os def main(): for i in range(5):...

Pass dynamic inventory to ansible-playbook: ansible-playbook -i inventory/dyn.py -l targethost my_playbook.yml python inventory/dyn.py should print out something like this: { "_meta": { "hostvars": { "10.1.0.10": { "ansible_user": ...

An integer will be interpreted as an index lookup. IceCream.objects.filter(metadata__buyer__known_for__0='creating stack overflow') See the note in the "Remarks" section about chaining queries.

Using subprocess.Popen give more fine-grained control over launched processes than subprocess.call. Launching a subprocess process = subprocess.Popen([r'C:\path\to\app.exe', 'arg1', '--flag', 'arg']) The signature for Popen is very similar to the call function; however, Popen will return immedi...

The vast majority of Python memory management is handled with reference counting. Every time an object is referenced (e.g. assigned to a variable), its reference count is automatically increased. When it is dereferenced (e.g. variable goes out of scope), its reference count is automatically decreas...

The only time the garbage collector is needed is if you have a reference cycle. The simples example of a reference cycle is one in which A refers to B and B refers to A, while nothing else refers to either A or B. Neither A or B are accessible from anywhere in the program, so they can safely be dest...

Inventory is the Ansible way to track all the systems in your infrastructure. Here is a simple inventory file containing a single system and the login credentials for Ansible. [targethost] 192.168.1.1 ansible_user=mrtuovinen ansible_ssh_pass=PassW0rd

[targethost] 192.168.1.1 ansible_user=mrtuovinen ssh_private_key_file=~/.ssh/custom_key

[targethost] 192.168.1.1 ansible_user=mrtuovinen ansible_port=2222

Using the timeit module from the command line: > python -m timeit 'for x in xrange(50000): b = x**3' 10 loops, best of 3: 51.2 msec per loop > python -m timeit 'from math import pow' 'for x in xrange(50000): b = pow(x,3)' 100 loops, best of 3: 9.15 msec per loop The built-in ** operato...