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Using property() on classmethods
...te the property on the metaclass.
>>> class foo(object):
... _var = 5
... class __metaclass__(type): # Python 2 syntax for metaclasses
... pass
... @classmethod
... def getvar(cls):
... return cls._var
... @classmethod
... def setvar(cls, value):
.....
How to read a file in reverse order?
...A correct, efficient answer written as a generator.
import os
def reverse_readline(filename, buf_size=8192):
"""A generator that returns the lines of a file in reverse order"""
with open(filename) as fh:
segment = None
offset = 0
fh.seek(0, os.SEEK_END)
file...
What does pylint's “Too few public methods” message mean
...they hold.
If your class looks like this:
class MyClass(object):
def __init__(self, foo, bar):
self.foo = foo
self.bar = bar
Consider using a dictionary or a namedtuple instead. Although if a class seems like the best choice, use it. pylint doesn't always know what's best.
D...
What's a correct and good way to implement __hash__()?
What's a correct and good way to implement __hash__() ?
6 Answers
6
...
C# 5 async CTP: why is internal “state” set to 0 in generated code before EndAwait call?
... int num3 = state;
if (num3 == 1)
{
goto Label_ContinuationPoint;
}
if (state == -1)
{
return;
}
t = new SimpleAwaitable();
i = 0;
Label_ContinuationPoint:
while (i < 3)
{
//...
How do I get the number of elements in a list?
...objects with a "size" in Python, in particular, have an attribute called ob_size, where the number of elements in the object is cached. So checking the number of objects in a list is very fast.
But if you're checking if list size is zero or not, don't use len - instead, put the list in a boolean co...
How do I check OS with a preprocessor directive?
...ecks. Here are a few of them, with links to where they're found:
Windows
_WIN32 Both 32 bit and 64 bit
_WIN64 64 bit only
Unix (Linux, *BSD, Mac OS X)
See this related question on some of the pitfalls of using this check.
unix
__unix
__unix__
Mac OS X
__APPLE__
__MACH__
Both are de...
Safe characters for friendly url [closed]
...igits, hyphen, period, underscore, and tilde."
ALPHA DIGIT "-" / "." / "_" / "~"
Note that RFC 3986 lists fewer reserved punctuation marks than the older RFC 2396.
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When to use Comparable and Comparator
... | Comparable | Comparator
._______________________________________________________________________________
Is used to allow Collections.sort to work | yes | yes
Can compare multiple fields | yes ...
How to avoid explicit 'self' in Python?
...e, and always know whether you are accessing a member or not:
class A(some_function()):
def f(self):
self.member = 42
self.method()
That's the complete code! (some_function returns the type used as a base.)
Another, where the methods of a class are dynamically composed:
class B(objec...