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List of zeros in python [duplicate]
...tertools.repeat and [0] * n will create lists whose elements refer to same id. This is not a problem with immutable objects like integers or strings but if you try to create list of mutable objects like a list of lists ([[]] * n) then all the elements will refer to the same object.
a = [[]] * 10
a...
SQL server query to get the list of columns in a table along with Data types, NOT NULL, and PRIMARY
...
To avoid duplicate rows for some columns, use user_type_id instead of system_type_id.
SELECT
c.name 'Column Name',
t.Name 'Data type',
c.max_length 'Max Length',
c.precision ,
c.scale ,
c.is_nullable,
...
How to wait until an element exists?
...ationObserver api a bit complex so I've built a library, arrive.js, to provide a simpler api to listen for elements creation/removal.
– Uzair Farooq
Apr 17 '14 at 18:23
16
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How does a Linux/Unix Bash script know its own PID?
I have a script in Bash called Script.sh , and it needs to know its own PID (i.e. I need to get PID inside the Script.sh )
...
Rails server says port already used, how to kill that process?
...s what webrick normally uses), type this in your terminal to find out the PID of the process:
$ lsof -wni tcp:3000
Then, use the number in the PID column to kill the process:
$ kill -9 PID
share
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How to use Git Revert
...te as if the commit that has been reverted never existed. For example, consider the following simple example:
$ cd /tmp/example
$ git init
Initialized empty Git repository in /tmp/example/.git/
$ echo "Initial text" > README.md
$ git add README.md
$ git commit -m "initial commit"
[master (root-co...
Remove duplicated rows
...moval, either from specific columns/variables (as in this question) or considering all columns/variables. dplyr is part of the tidyverse.
Data and package
library(dplyr)
dat <- data.frame(a = rep(c(1,2),4), b = rep(LETTERS[1:4],2))
Remove rows duplicated in a specific column (e.g., columna)
...
Drawing an image from a data URL to a canvas
... Canvas Context lets you copy all or a portion of an image (or canvas, or video) onto a canvas.
You might use it like so:
var myCanvas = document.getElementById('my_canvas_id');
var ctx = myCanvas.getContext('2d');
var img = new Image;
img.onload = function(){
ctx.drawImage(img,0,0); // Or at wh...
Managing relationships in Laravel, adhering to the repository pattern
... your "business problem".
A Course is a "entity", with attributes (title, id, etc) and even other entities (Assignments, which have their own attributes and possibly entities).
Your "Course" repository should be able to return a Course and the Courses' attributes/Assignments (including Assignment)...
What is the difference between “INNER JOIN” and “OUTER JOIN”?
...ally show any distinction between different types of join predicate or provide a framework for reasoning about how they will operate.
There is no substitute for understanding the logical processing and it is relatively straightforward to grasp anyway.
Imagine a cross join.
Evaluate the on clause ag...