Tutorial by Examples: re

A random forest is a meta estimator that fits a number of decision tree classifiers on various sub-samples of the dataset and use averaging to improve the predictive accuracy and control over-fitting. A simple usage example: Import: from sklearn.ensemble import RandomForestClassifier Define tr...

Sometimes repos will have commits that only adjust whitespace, for example fixing indentation or switching between tabs and spaces. This makes it difficult to find the commit where the code was actually written. git blame -w will ignore whitespace-only changes to find where the line really came fr...

One of the uses of recursion is to navigate through a hierarchical data structure, like a file system directory tree, without knowing how many levels the tree has or the number of objects on each level. In this example, you will see how to use recursion on a directory tree to find all sub-directorie...

It is a good idea to maintain a web-scraping session to persist the cookies and other parameters. Additionally, it can result into a performance improvement because requests.Session reuses the underlying TCP connection to a host: import requests with requests.Session() as session: # all req...

Because LINQ uses deferred execution, we can have a query object that doesn't actually contain the values, but will return the values when evaluated. We can thus dynamically build the query based on our control flow, and evaluate it once we are finished: IEnumerable<VehicleModel> BuildQuery(i...

To get the value of the last result from your last expression in the console, use an underscore _. >>> 2 + 2 4 >>> _ 4 >>> _ + 6 10 This magic underscore value is only updated when using a python expression that results in a value. Defining functions or for loops ...

The For Each loop construct is ideal for iterating all elements of a collection. Public Sub IterateCollection(ByVal items As Collection) 'For Each iterator must always be variant Dim element As Variant For Each element In items 'assumes element can be converted to a stri...

Postfix increment X++ will add 1 to x var x = 42; x++; Console.WriteLine(x); // 43 Postfix decrement X-- will subtract one var x = 42 x--; Console.WriteLine(x); // 41 ++x is called prefix increment it increments the value of x and then returns x while x++ returns the value of x and the...

Predefined operators according to ISO/IEC 13211-1 and 13211-2: PriorityTypeOperator(s)Use1200xfx:- -->1200fx:- ?-Directive, query1100xfy;1050xfy->1000xfy','900fy\+700xfx= \\=Term unification700xfx== \\== @< @=< @> @>=Term comparison700xfx=..700xfxis =:= =\= < > =<...

vagrant up --provider vmware_fusion

vagrant up --provider vmware_workstation

vagrant snapshot restore mysnapshot

vagrant snapshot restore --no-provision mysnapshot

vagrant snapshot delete mysnapshot

If perror is not flexible enough, you may obtain a user-readable error description by calling strerror from <string.h>. int main(int argc, char *argv[]) { FILE *fout; int last_error = 0; if ((fout = fopen(argv[1], "w")) == NULL) { last_error = errno; ...

Generates a storable representation of a value. This is useful for storing or passing PHP values around without losing their type and structure. To make the serialized string into a PHP value again, use unserialize(). Serializing a string $string = "Hello world"; echo serialize($s...

Problem # models.py: class Library(models.Model): name = models.CharField(max_length=100) books = models.ManyToManyField(Book) class Book(models.Model): title = models.CharField(max_length=100) # views.py def myview(request): # Query the database. libraries = Librar...

Problem Django querysets are evaluated in a lazy fashion. For example: # models.py: class Author(models.Model): name = models.CharField(max_length=100) class Book(models.Model): author = models.ForeignKey(Author, related_name='books') title = models.CharField(max_length=100) ...

If you return a prvalue expression from a function, and the prvalue expression has the same type as the function's return type, then the copy from the prvalue temporary can be elided: std::string func() { return std::string("foo"); } Pretty much all compilers will elide the tempor...

When you pass an argument to a function, and the argument is a prvalue expression of the function's parameter type, and this type is not a reference, then the prvalue's construction can be elided. void func(std::string str) { ... } func(std::string("foo")); This says to create a tem...