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Creating a singleton in Python
...mple implementation:
class Singleton(type):
_instances = {}
def __call__(cls, *args, **kwargs):
if cls not in cls._instances:
cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
return cls._instances[cls]
class Logger(object):
__meta...
PATH issue with pytest 'ImportError: No module named YadaYadaYada'
I used easy_install to install pytest on a mac and started writing tests for a project with a file structure likes so:
20 A...
Iterate over object attributes in python
...foo = 1
... bar = 'hello'
... def func(self):
... return 'call me'
...
>>> obj = Cls()
calling dir on the object gives you back all the attributes of that object, including python special attributes. Although some object attributes are callable, such as methods.
>>&...
How to disable GCC warnings for a few lines of code
...n GCC and Clang.
Consider the following Makefile
CPPFLAGS:=-std=c11 -W -Wall -pedantic -Werror
.PHONY: all
all: puts
for building the following puts.c source code
#include <stdio.h>
int main(int argc, const char *argv[])
{
while (*++argv) puts(*argv);
return 0;
}
It will not c...
How to find the size of localStorage
...ly developing a site that will make use of HTML5's localStorage. I've read all about the size limitations for different browsers. However, I haven't seen anything on how to find out the current size of a localStorage instance. This question seems to indicate that JavaScript doesn't have a built in...
How can you set class attributes from variable arguments (kwargs) in python
...riable number of arguments and then sets them as class attributes conditionally.
10 Answers
...
How to enumerate an object's properties in Python?
...oes not return dynamic members (i.e., object attributes and methods dynamically defined by that object's __getattr__() method or similar magic). In all likelihood, your desired file.ImplementationName property is defined dynamically and hence not available to vars() or dir().
–...
Inheritance and Overriding __init__ in python
...
The book is a bit dated with respect to subclass-superclass calling. It's also a little dated with respect to subclassing built-in classes.
It looks like this nowadays:
class FileInfo(dict):
"""store file metadata"""
def __init__(self, filename=None):
super(FileInfo,...
Build a Basic Python Iterator
...
Iterator objects in python conform to the iterator protocol, which basically means they provide two methods: __iter__() and __next__().
The __iter__ returns the iterator object and is implicitly called
at the start of loops.
The __next__() method returns the next value and is implicitly cal...
Why use Abstract Base Classes in Python?
...emented classes.
Long version
There is a contract between a class and its callers. The class promises to do certain things and have certain properties.
There are different levels to the contract.
At a very low level, the contract might include the name of a method or its number of parameters.
In a s...