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How to make a class property? [duplicate]
...re's how I would do this:
class ClassPropertyDescriptor(object):
def __init__(self, fget, fset=None):
self.fget = fget
self.fset = fset
def __get__(self, obj, klass=None):
if klass is None:
klass = type(obj)
return self.fget.__get__(obj, klass)(...
Python dictionary from an object's fields
...s'. To build a dictionary from an arbitrary object, it's sufficient to use __dict__. Usually, you'll declare your methods at class level and your attributes at instance level, so __dict__ should be fine. For example:
>>> class A(object):
... def __init__(self):
... self.b = 1
... ...
Evaluating a mathematical expression in a string
...I've rewrapped fourFn into a numeric parser class for easier reuse.
from __future__ import division
from pyparsing import (Literal, CaselessLiteral, Word, Combine, Group, Optional,
ZeroOrMore, Forward, nums, alphas, oneOf)
import math
import operator
__author__ = 'Paul McGu...
Difference between left join and right join in SQL Server [duplicate]
... two table with following records:
Table A
id firstname lastname
___________________________
1 Ram Thapa
2 sam Koirala
3 abc xyz
6 sruthy abc
Table B
id2 place
_____________
1 Nepal
2 USA
3 Lumbini
5 Kathmandu
Inne...
What exactly does += do in python?
...
In Python, += is sugar coating for the __iadd__ special method, or __add__ or __radd__ if __iadd__ isn't present. The __iadd__ method of a class can do anything it wants. The list object implements it and uses it to iterate over an iterable object appending each...
Shards and replicas in Elasticsearch
... elasticsearch will create 5 primary shards that will contain your data:
____ ____ ____ ____ ____
| 1 | | 2 | | 3 | | 4 | | 5 |
|____| |____| |____| |____| |____|
Every time you index a document, elasticsearch will decide which primary shard is supposed to hold that docu...
Is it possible to make abstract classes in Python?
...
# Python 2
from abc import ABCMeta, abstractmethod
class Abstract:
__metaclass__ = ABCMeta
@abstractmethod
def foo(self):
pass
Whichever way you use, you won't be able to instantiate an abstract class that has abstract methods, but will be able to instantiate a subclass th...
How do I get the full path of the current file's directory?
...3
For the directory of the script being run:
import pathlib
pathlib.Path(__file__).parent.absolute()
For the current working directory:
import pathlib
pathlib.Path().absolute()
Python 2 and 3
For the directory of the script being run:
import os
os.path.dirname(os.path.abspath(__file__))
I...
Why do some functions have underscores “__” before and after the function name?
...gnized (these can generally be combined with any case convention):
_single_leading_underscore: weak "internal use" indicator. E.g. from M import * does not import objects whose name starts with an underscore.
single_trailing_underscore_: used by convention to avoid conflicts with Python ke...
Is module __file__ attribute absolute or relative?
I'm having trouble understanding __file__ . From what I understand, __file__ returns the absolute path from which the module was loaded.
...