In Python 3.x, the correct way to check if s is a string is isinstance(s, str) The bytes class isn’t considered a string type in Python 3. In Python 2.x, the correct check was isinstance(s, basestring) basestring is the abstract superclass of str and unicode. It can be used to test whether an object is … Read more
See Python PEP 8: Function and Variable Names: Function names should be lowercase, with words separated by underscores as necessary to improve readability. Variable names follow the same convention as function names. mixedCase is allowed only in contexts where that’s already the prevailing style (e.g. threading.py), to retain backwards compatibility.
In JavaScript, null is an object. There’s another value for things that don’t exist, undefined. The DOM returns null for almost all cases where it fails to find some structure in the document, but in JavaScript itself undefined is the value used. Second, no, there is not a direct equivalent. If you really want to … Read more
A simple answer is: echo ” lol ” | xargs Xargs will do the trimming for you. It’s one command/program, no parameters, returns the trimmed string, easy as that! Note: this doesn’t remove all internal spaces so “foo bar” stays the same; it does NOT become “foobar”. However, multiple spaces will be condensed to single … Read more
To check the existence of a local variable: if ‘myVar’ in locals(): # myVar exists. To check the existence of a global variable: if ‘myVar’ in globals(): # myVar exists. To check if an object has an attribute: if hasattr(obj, ‘attr_name’): # obj.attr_name exists.
Notice / Warning: Undefined variable From the vast wisdom of the PHP Manual: Relying on the default value of an uninitialized variable is problematic in the case of including one file into another which uses the same variable name. It is also a major security risk with register_globals turned on. E_NOTICE level error is issued … Read more
There are several ways of checking if an variable is an array or not. The best solution is the one you have chosen. variable.constructor === Array This is the fastest method on Chrome, and most likely all other browsers. All arrays are objects, so checking the constructor property is a fast process for JavaScript engines. … Read more
(Usually) The right way if [ -z ${var+x} ]; then echo “var is unset”; else echo “var is set to ‘$var'”; fi where ${var+x} is a parameter expansion which evaluates to nothing if var is unset, and substitutes the string x otherwise. Quotes Digression Quotes can be omitted (so we can say ${var+x} instead of … Read more
TLDR JavaScript has lexical (also called static) scoping and closures. This means you can tell the scope of an identifier by looking at the source code. The four scopes are: Global – visible by everything Function – visible within a function (and its sub-functions and blocks) Block – visible within a block (and its sub-blocks) … Read more
You want the typeof operator. Specifically: if (typeof variable !== ‘undefined’) { // the variable is defined }