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Example for reading file data_file.csv such as: File: index,header1,header2,header3 1,str_data,12,1.4 3,str_data,22,42.33 4,str_data,2,3.44 2,str_data,43,43.34 7, str_data, 25, 23.32 Code: pd.read_csv('data_file.csv') Output: index header1 header2 header3 0 1 str_dat...

Once your virtual environment has been activated, any package that you install will now be installed in the virtualenv & not globally. Hence, new packages can be without needing root privileges. To verify that the packages are being installed into the virtualenv run the following command to che...

Assuming python and python3 are both installed, it is possible to create a virtual environment for Python 3 even if python3 is not the default Python: virtualenv -p python3 foo or virtualenv --python=python3 foo or python3 -m venv foo or pyvenv foo Actually you can create virtual ...

Properties are members of an object. Each named property is a pair of (name, descriptor). The name is a string that allows access (using the dot notation object.propertyName or the square brackets notation object['propertyName']). The descriptor is a record of fields defining the bevahiour of the pr...

By default error message appears below textbox in <div class="help-block"></div> on keyUp or after pressing submit button if any validation constraints aren't met. Sometimes we want a message on submit only i.e. no validation at onKeyup event. Let's check yii2/widgets/ActiveF...

An interface in Kotlin can have default implementations for functions: interface MyInterface { fun withImplementation() { print("withImplementation() was called") } } Classes implementing such interfaces will be able to use those functions without reimplementing cl...

There are several ways methods can be inherited public abstract class Car { public void HonkHorn() { // Implementation of horn being honked } // virtual methods CAN be overridden in derived classes public virtual void ChangeGear() { // Implementation of gear...

You don't have to check the IDisposable object for null. using will not throw an exception and Dispose() will not be called: DisposableObject TryOpenFile() { return null; } // disposable is null here, but this does not throw an exception using (var disposable = TryOpenFile()) { //...

Java 8 provides classes called IntSummaryStatistics, DoubleSummaryStatistics and LongSummaryStatistics which give a state object for collecting statistics such as count, min, max, sum, and average. Java SE 8 List<Integer> naturalNumbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); IntSu...

Pseudo-elements are added to selectors but instead of describing a special state, they allow you to style certain parts of a document. The content attribute is required for pseudo-elements to render; however, the attribute can have an empty value (e.g. content: ""). div::after { conte...

Another neat feature using slices is slice assignment. Python allows you to assign new slices to replace old slices of a list in a single operation. This means that if you have a list, you can replace multiple members in a single assignment: lst = [1, 2, 3] lst[1:3] = [4, 5] print(lst) # Out: [1...

$fruit1 = ['apples', 'pears']; $fruit2 = ['bananas', 'oranges']; $all_of_fruits = array_merge($fruit1, $fruit2); // now value of $all_of_fruits is [0 => 'apples', 1 => 'pears', 2 => 'bananas', 3 => 'oranges'] Note that array_merge will change numeric indexes, but overwrite string...

A context manager is an object that is notified when a context (a block of code) starts and ends. You commonly use one with the with statement. It takes care of the notifying. For example, file objects are context managers. When a context ends, the file object is closed automatically: open_file = ...

In Python 2, an iterator can be traversed by using a method called next on the iterator itself: Python 2.x2.3 g = (i for i in range(0, 3)) g.next() # Yields 0 g.next() # Yields 1 g.next() # Yields 2 In Python 3 the .next method has been renamed to .__next__, acknowledging its “magic” ro...

The null coalescing operator makes it easy to ensure that a method that may return null will fall back to a default value. Without the null coalescing operator: string name = GetName(); if (name == null) name = "Unknown!"; With the null coalescing operator: string name = GetN...

enum MyEnum { One, Two, Three } foreach(MyEnum e in Enum.GetValues(typeof(MyEnum))) Console.WriteLine(e); This will print: One Two Three

Running the latest Liferay CE is straightforward: Go to https://www.liferay.com/downloads. Choose a bundle among the ones listed. For beginners, the Tomcat bundle is a good choice. Click in "Download." Unzip the download package whenever you find fit. The unzipped directory will...

You can use a column's number (where the leftmost column is '1') to indicate which column to base the sort on, instead of describing the column by its name. Pro: If you think it's likely you might change column names later, doing so won't break this code. Con: This will generally reduce readabilit...

A custom exception is any class that extends Exception or a subclass of Exception. In general, you should always extend StandardError or a descendant. The Exception family are usually for virtual-machine or system errors, rescuing them can prevent a forced interruption from working as expected. # ...

You can set the timezone that will be used by Django in the settings.py file. Examples: TIME_ZONE = 'UTC' # use this, whenever possible TIME_ZONE = 'Europe/Berlin' TIME_ZONE = 'Etc/GMT+1' Here is the list of valid timezones When running in a Windows environment this must be set to the same a...