Tutorial by Examples: s

Your code will not work in projects where you reference the User model (and where the AUTH_USER_MODEL setting has been changed) directly. For example: if you want to create Post model for a blog with a customized User model, you should specify the custom User model like this: from django.conf impo...

jQuery accepts a wide variety of parameters as "selectors", and one of them is an HTML string. Passing an HTML string to jQuery will cause the underlying array-like structure of the jQuery object to hold the resulting constructed HTML. jQuery uses regex to determine if the string being pa...

from scipy.stats import rv_continuous import numpy class Neg_exp(rv_continuous): def _cdf(self, x, lamda): return 1-numpy.exp(-lamda*x) neg_exp = Neg_exp(name="Negative exponential", a=0) print (neg_exp.pdf(0,.5)) print (neg_exp.pdf(5,.5)) print (neg_exp.cdf(5...

There are many reasons a write operation may fail. A frequent one is because your security rules reject the operation, for example because you're not authenticated (by default a database can only be accessed by an authenticated user). You can see these security rule violations in the output of your...

SQL Server 2008 The ROW_NUMBER function can assign an incrementing number to each row in a result set. Combined with a Common Table Expression that uses a BETWEEN operator, it is possible to create 'pages' of result sets. For example: page one containing results 1-10, page two containing results 11...

SQL Server 2012 The OFFSET FETCH clause implements pagination in a more concise manner. With it, it's possible to skip N1 rows (specified in OFFSET) and return the next N2 rows (specified in FETCH): SELECT * FROM sys.objects ORDER BY object_id OFFSET 40 ROWS FETCH NEXT 10 ROWS ONLY The ORDER...

// It's possible to unpack tuples to assign their inner values to variables let tup = (0, 1, 2); // Unpack the tuple into variables a, b, and c let (a, b, c) = tup; assert_eq!(a, 0); assert_eq!(b, 1); // This works for nested data structures and other complex data types let complex = ((1,...

Writing a gzipped file To write a gzipped file, use the module IO::Compress::Gzip and create a filehandle by creating a new instance of IO::Compress::Gzip for the desired output file: use strict; use warnings; use open qw( :encoding(UTF-8) :std ); # Make UTF-8 default encoding use IO::Compres...

HTML DOM is Expensive Each web page is represented internally as a tree of objects. This representation is called Document Object Model. Moreover, it is a language-neutral interface that allows programming languages (such as JavaScript) to access the HTML elements. In other words The HTML DOM...

Generating the minimum number of operations to transform one tree into another have a complexity in the order of O(n^3) where n is the number of nodes in the tree. React relies on two assumptions to solve this problem in a linear time - O(n) Two components of the same class will generate sim...

When two nodes are not of the same type, React doesn't try to match them - it just removes the first node from the DOM and inserts the second one. This is why the first tip says If you see yourself alternating between two components classes with very similar output, you may want to make it the sa...

Recommended way to install Slim framework is by using composer. Create an empty directory This directory will contain all required files for our Slim application to run. We call this directory root directory so we can address all other application files and directories relative to root directo...

ContactManager contactManager = Factory.CreateObject("tracking/contactManager", true) as ContactManager; Contact contact = contactManager.LoadContactReadOnly(userName); return contact;

This method doesn't require initialization of the tracker, which is handy if the state should be changed outside of the site context (for example in the shell). var stateManager = AutomationStateManager.Create(contact); automationStateManager.MoveToEngagementState(stateItem.ParentID, stateId); st...

Sometimes, it's better to have only three options style="@android:style/TextAppearance.Small" style="@android:style/TextAppearance.Medium" style="@android:style/TextAppearance.Large" Use small and large to differentiate from normal screen size. <TextView ...

When you join two tables, SQL Server query optimizer (QO) can choose different types of joins that will be used in query: HASH join LOOP join MERGE join QO will explore plans and choose the optimal operator for joining tables. However, if you are sure that you know what would be the optimal ...

When you use GROUP BY clause, SQL Server query optimizer (QO) can choose different types of grouping operators: HASH Aggregate that creates hash-map for grouping entries Stream Aggregate that works well with pre-ordered inputs You can explicitly require that QO picks one or another aggregate ...

Specifies that the query is optimized for fast retrieval of the first number_rows. This is a nonnegative integer. After the first number_rows are returned, the query continues execution and produces its full result set. select OrderID, AVG(Quantity) from Sales.OrderLines group by OrderID OPTION ...

When you use UNION operator on two query results, Query optimizer (QO) can use following operators to create a union of two result sets: Merge (Union) Concat (Union) Hash Match (Union) You can explicitly specify what operator should be used using OPTION() hint: select OrderID, OrderDate, Ex...

By using the method GET_SUBMATCH of class CL_ABAP_MATCHER, we can get the data in the groups/subgroups. Goal: get the token to the right of the keyword 'Type'. DATA: lv_pattern TYPE string VALUE 'type\s+(\w+)', lv_test TYPE string VALUE 'data lwa type mara'. CREATE OBJECT ref_regex EX...