Tutorial by Examples: s

use std::io::{Read, Result as IoResult}; use std::fs::File; struct Config(u8); fn read_config() -> IoResult<String> { let mut s = String::new(); let mut file = File::open(&get_local_config_path()) // or_else closure is invoked if Result is Err. .or_els...

EXTENDED_ARG = 145 # All opcodes greater than this have 2 operands HAVE_ARGUMENT = 90 # All opcodes greater than this have at least 1 operands cmp_op = ('<', '<=', '==', '!=', '>', '>=', 'in', 'not in', 'is', 'is ... # A list of comparator id's. The indecies are used as opera...

Python is a hybrid interpreter. When running a program, it first assembles it into bytecode which can then be run in the Python interpreter (also called a Python virtual machine). The dis module in the standard library can be used to make the Python bytecode human-readable by disassembling classes, ...

To disassemble a Python module, first this has to be turned into a .pyc file (Python compiled). To do this, run python -m compileall <file>.py Then in an interpreter, run import dis import marshal with open("<file>.pyc", "rb") as code_f: code_f.read(8) # M...

The iloc (short for integer location) method allows to select the rows of a dataframe based on their position index. This way one can slice dataframes just like one does with Python's list slicing. df = pd.DataFrame([[11, 22], [33, 44], [55, 66]], index=list("abc")) df # Out: # 0...

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

Trap expressions don't have to be individual functions or programs, they can be more complex expressions as well. By combining jobs -p and kill, we can kill all spawned child processes of the shell on exit: trap 'jobs -p | xargs kill' EXIT

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...

The typing.TypeVar is a generic type factory. It's primary goal is to serve as a parameter/placeholder for generic function/class/method annotations: import typing T = typing.TypeVar("T") def get_first_element(l: typing.Sequence[T]) -> T: """Gets the first ele...

Enum constants are instantiated when an enum is referenced for the first time. Therefore, that allows to implement Singleton software design pattern with a single-element enum. public enum Attendant { INSTANCE; private Attendant() { // perform some initialization routine ...

To get basic information about a DataFrame including the column names and datatypes: import pandas as pd df = pd.DataFrame({'integers': [1, 2, 3], 'floats': [1.5, 2.5, 3], 'text': ['a', 'b', 'c'], 'ints with None': [1, None, 3]}) ...

df = pd.DataFrame({'a': [1, 2, 3], 'b': [4, 5, 6], 'c': [7, 8, 9]}) To list the column names in a DataFrame: >>> list(df) ['a', 'b', 'c'] This list comprehension method is especially useful when using the debugger: >>> [c for c in df] ['a', 'b', 'c'] This is the long w...

NuGet version Before you start: make sure your NuGet version is up to date. In Visual Studio, go to Tools > Extensions and Updates, then Updates > Visual Studio Gallery. Check if there is a NuGet Update available and install it. Or, you can uninstall the existing nuget and reinstall it. It w...

End a line with two or more spaces to create a line break. Ending a line with no spaces or with just one space doesn't create a line beak. Use two or more spaces to create a line break. Use an empty line to make a new paragraph. Ending a line with no spaces or with just one space...

SilverStripe can be installed via composer or through the extraction of downloaded zip file. To install through composer we run the following command composer create-project silverstripe/installer /path/to/project 3.4.0 A download zip file can be found on the download page of the SilverStripe w...

In Fortran functions and subroutines need to be explicitly declared as recursive, if they are to call themselves again, directly or indirectly. Thus, a recursive implementation of the Fibonacci series could look like this: recursive function fibonacci(term) result(fibo) integer, intent(in) :: te...

It is possible to detect whether an operator or function can be called on a type. To test if a class has an overload of std::hash, one can do this: #include <functional> // for std::hash #include <type_traits> // for std::false_type and std::true_type #include <utility> // for s...

You can validate any object, even plain ruby. class User include ActiveModel::Validations attr_reader :name, :age def initialize(name, age) @name = name @age = age end validates :name, presence: true validates :age, numericality: { only_integer: true, greater_than...