What is the difference between old style and new style classes in Python? When should I use one or the other? 8 s 8 From New-style and classic classes: Up to Python 2.1, old-style classes were the only flavour available to the user. The concept of (old-style) class is unrelated to the concept of type: … Read more
I’ve come across this term POD-type a few times. What does it mean? 9 s 9 POD stands for Plain Old Data – that is, a class (whether defined with the keyword struct or the keyword class) without constructors, destructors and virtual members functions. Wikipedia’s article on POD goes into a bit more detail and … Read more
I want to convert a table, represented as a list of lists, into a pandas DataFrame. As an extremely simplified example: a = [[‘a’, ‘1.2’, ‘4.2’], [‘b’, ’70’, ‘0.03’], [‘x’, ‘5’, ‘0’]] df = pd.DataFrame(a) What is the best way to convert the columns to the appropriate types, in this case columns 2 and 3 … Read more
What are the differences between these two code snippets? Using type(): import types if type(a) is types.DictType: do_something() if type(b) in types.StringTypes: do_something_else() Using isinstance(): if isinstance(a, dict): do_something() if isinstance(b, str) or isinstance(b, unicode): do_something_else() 7 To summarize the contents of other (already good!) answers, isinstance caters for inheritance (an instance of a derived … Read more
I’ve seen many people use the following code: Type t = typeof(obj1); if (t == typeof(int)) // Some code here But I know you could also do this: if (obj1.GetType() == typeof(int)) // Some code here Or this: if (obj1 is int) // Some code here Personally, I feel the last one is the cleanest, … Read more
How do you check if a value is an object in JavaScript? 4 49
Example (note the case): string s = “Hello world!”; String s = “Hello world!”; What are the guidelines for the use of each? And what are the differences? 6 63
Long is the Object form of long, and Integer is the object form of int. The long uses 64 bits. The int uses 32 bits, and so can only hold numbers up to ±2 billion (-231 to +231-1). You should use long and int, except where you need to make use of methods inherited from Object, such as hashcode. Java.util.collections methods usually use the boxed (Object-wrapped) versions, because they need to work for any Object, and … Read more
What is the best way to check whether a given object is of a given type? How about checking whether the object inherits from a given type? Let’s say I have an object o. How do I check whether it’s a str? 1 14
How do I see the type of a variable? (e.g. unsigned 32 bit) 1 19
