Tutorial by Examples: re

Boolean logic expressions, in addition to evaluating to True or False, return the value that was interpreted as True or False. It is Pythonic way to represent logic that might otherwise require an if-else test. And operator The and operator evaluates all expressions and returns the last expressi...

Say we have the following tree: root - A - AA - AB - B - BA - BB - BBA Now, if we wish to list all the names of the elements, we could do this with a simple for-loop. We assume there is a function get_name() to return a string of the name of a node, a function get_children() t...

If you have your data stored in a list and you want to convert this list to a data frame the do.call function is an easy way to achieve this. However, it is important that all list elements have the same length in order to prevent unintended recycling of values. dataList <- list(1:3,4:6,7:9) ...

class PostsController < ApplicationController before_action :set_post, only: [:show, :edit, :update, :destroy] def index @posts = Post.all end def show end def new @post = Post.new end def edit end def create @post = Post.new(post_par...

You can create your ssh key using ssh-keygen, it's a program that is part of the ssh installation. To do so just run it and follow the instructions on screen. Here's an example: $ ssh-keygen Generating public/private rsa key pair. The default directory where you ssh key pair will be saved is i...

To increase the maximum amount of heap memory used Eclipse, edit the eclipse.ini file located in the Eclipse installation directory. This file specifies options for the startup of Eclipse, such as which JVM to use, and the options for the JVM. Specifically, you need to edit the value of the -Xmx JV...

class File(): def __init__(self, filename, mode): self.filename = filename self.mode = mode def __enter__(self): self.open_file = open(self.filename, self.mode) return self.open_file def __exit__(self, *args): self.open_file.close() ...

Similar to the built-in function zip(), itertools.zip_longest will continue iterating beyond the end of the shorter of two iterables. from itertools import zip_longest a = [i for i in range(5)] # Length is 5 b = ['a', 'b', 'c', 'd', 'e', 'f', 'g'] # Length is 7 for i in zip_longest(a, b): x...

Who says you cannot throw multiple exceptions in one method. If you are not used to playing around with AggregateExceptions you may be tempted to create your own data-structure to represent many things going wrong. There are of course were another data-structure that is not an exception would be mor...

CSV(Comma Separated Values) is a simple file format used to store tabular data, such as a spreadsheet. This is a minimal example of how to write & read data in Python. Writing data to a CSV file: import csv data = [["Ravi", "9", "550"], ["Joe", "8...

Example for continue for i in [series] do command 1 command 2 if (condition) # Condition to jump over command 3 continue # skip to the next value in "series" fi command 3 done Example for break for i in [series] do command 4 if (condi...

Keyword lists are tuples of key/value, generally used as options for a function call. [{:a, 1}, {:b, 2}] // creates a non-empty keyword list Keyword lists can have the same key repeated more than once. [{:a, 1}, {:a, 2}, {:b, 2}] [{:a, 1}, {:b, 2}, {:a, 2}] Keys and values can be any type: ...

When Intel defined the original 8086, it was a 16-bit processor with a 20-bit address bus (see below). They defined 8 general-purpose 16-bit registers - but gave them specific roles for certain instructions: AX The Accumulator register. Many opcodes either assumed this register, or were faster i...

When Intel produced the 80386, they upgraded from a 16-bit processor to a 32-bit one. 32-bit processing means two things: both the data being manipulated was 32-bit, and the memory addresses being accessed were 32-bit. To do this, but still remain compatible with their earlier processors, they intro...

The first four 16-bit registers could have their upper- and lower-half bytes accessed directly as their own registers: AH and AL are the High and Low halves of the AX register. BH and BL are the High and Low halves of the BX register. CH and CL are the High and Low halves of the CX register. D...

Segmentation When Intel was designing the original 8086, there were already a number of 8-bit processors that had 16-bit capabilities - but they wanted to produce a true 16-bit processor. They also wanted to produce something better and more capable than what was already out there, so they wanted t...

AMD is a processor manufacturer that had licensed the design of the 80386 from Intel to produce compatible - but competing - versions. They made internal changes to the design to improve throughput or other enhancements to the design, while still being able to execute the same programs. To one-up I...

When the x86 Arithmetic Logic Unit (ALU) performs operations like NOT and ADD, it flags the results of these operations ("became zero", "overflowed", "became negative") in a special 16-bit FLAGS register. 32-bit processors upgraded this to 32 bits and called it EFLAGS, ...

(defun foobar (x y) (format t "X: ~s~@ Y: ~s~%" x y)) (foobar 10 20) ; X: 10 ; Y: 20 ;=> NIL

A single rest-parameter can be given with the keyword &REST after the required arguments. If such a parameter exists, the function can take a number of arguments, which will be grouped into a list in the rest-parameter. Note that the variable CALL-ARGUMENTS-LIMIT determines the maximum number of...