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Python __str__ versus __unicode__
Is there a python convention for when you should implement __str__() versus __unicode__() . I've seen classes override __unicode__() more frequently than __str__() but it doesn't appear to be consistent. Are there specific rules when it is better to implement one versus the other? Is it ne...
Define a lambda expression that raises an Exception
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There is more than one way to skin a Python:
y = lambda: (_ for _ in ()).throw(Exception('foobar'))
Lambdas accept statements. Since raise ex is a statement, you could write a general purpose raiser:
def raise_(ex):
raise ex
y = lambda: raise_(Exception('foobar'))
But if...
How to upload files to server using JSP/Servlet?
....xml file:
http://joseluisbz.wordpress.com/2014/01/17/manually-installing-php-tomcat-and-httpd-lounge/#Enabling%20File%20Uploads.
<servlet>
<servlet-name>jsp</servlet-name>
<servlet-class>org.apache.jasper.servlet.JspServlet</servlet-class>
<multipart-c...
Is there a Python caching library?
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From Python 3.2 you can use the decorator @lru_cache from the functools library.
It's a Last Recently Used cache, so there is no expiration time for the items in it, but as a fast hack it's very useful.
from functools import lru_cache
@lru_cache(maxsize=256)
def f(x):
...
Python extending with - using super() Python 3 vs Python 2
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super() (without arguments) was introduced in Python 3 (along with __class__):
super() -> same as super(__class__, self)
so that would be the Python 2 equivalent for new-style classes:
super(CurrentClass, self)
for old-style classes you can always use:
class Classname(OldStyleParen...
what does the __file__ variable mean/do?
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When a module is loaded from a file in Python, __file__ is set to its path. You can then use that with other functions to find the directory that the file is located in.
Taking your examples one at a time:
A = os.path.join(os.path.dirname(__file__), '..')
# A is the par...
SQL SELECT WHERE field contains words
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This move was incredible ,, I am Really JEALOUS :( _______________________________________________________________________________________ INNER JOIN (@FilterTable F1 ON T.Column1 LIKE '%' + F1.Data + '%' LEFT JOIN (@FilterTable F2 ON T.Column1 NOT LIKE '%' + F2.Data + ...
How to create a custom string representation for a class object?
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Implement __str__() or __repr__() in the class's metaclass.
class MC(type):
def __repr__(self):
return 'Wahaha!'
class C(object):
__metaclass__ = MC
print C
Use __str__ if you mean a readable stringification, use __repr__ fo...
PostgreSQL: Difference between text and varchar (character varying)
...ength array).
Check this article from Depesz: http://www.depesz.com/index.php/2010/03/02/charx-vs-varcharx-vs-varchar-vs-text/
A couple of highlights:
To sum it all up:
char(n) – takes too much space when dealing with values shorter than n (pads them to n), and can lead to subtle err...
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...