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Remove all occurrences of a value from a list?
...ython 3.x
>>> x = [1,2,3,2,2,2,3,4]
>>> list(filter((2).__ne__, x))
[1, 3, 3, 4]
or
>>> x = [1,2,3,2,2,2,3,4]
>>> list(filter(lambda a: a != 2, x))
[1, 3, 3, 4]
Python 2.x
>>> x = [1,2,3,2,2,2,3,4]
>>> filter(lambda a: a != 2, x)
[1, 3, 3...
namedtuple and default values for optional keyword arguments
...Node()
Node(val=None, left=None, right=None)
Before Python 3.7
Set Node.__new__.__defaults__ to the default values.
>>> from collections import namedtuple
>>> Node = namedtuple('Node', 'val left right')
>>> Node.__new__.__defaults__ = (None,) * len(Node._fields)
>&g...
What does $_ mean in PowerShell?
...ich is called $PSItem in Powershell 3 and newer.
1,2,3 | %{ write-host $_ }
or
1,2,3 | %{ write-host $PSItem }
For example in the above code the %{} block is called for every value in the array. The $_ or $PSItem variable will contain the current value.
...
Where should signal handlers live in a django project?
...ke:
yourapp/signals/handlers.py:
from django.db.models.signals import pre_save
from django.dispatch import receiver
from myapp.models import MyModel
@receiver(pre_save, sender=MyModel)
def my_handler(sender, **kwargs):
pass
The best place to register your signal handler is then in the AppCo...
Understanding Python super() with __init__() methods [duplicate]
...ady.
Note that the syntax changed in Python 3.0: you can just say super().__init__() instead of super(ChildB, self).__init__() which IMO is quite a bit nicer. The standard docs also refer to a guide to using super() which is quite explanatory.
...
Python hashable dicts
...another dictionary for obvious reasons.
class hashabledict(dict):
def __hash__(self):
return hash(tuple(sorted(self.items())))
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How to duplicate sys.stdout to a log file?
...ileno())
print "\nstdout"
print >>sys.stderr, "stderr"
os.spawnve("P_WAIT", "/bin/ls", ["/bin/ls"], {})
os.execve("/bin/ls", ["/bin/ls"], os.environ)
You could also emulate tee using the multiprocessing package (or use processing if you're using Python 2.5 or earlier).
Update
Here is a Py...
Why would you use an ivar?
...d by the compiler may involve another C function call to the functions objc_getProperty/objc_setProperty, as these will have to retain/copy/autorelease the objects as needed and further perform spinlocking for atomic properties where necessary. This can easily get very expensive and I'm not talking ...
Mongoose, Select a specific field with find
...
The _id field is always present unless you explicitly exclude it. Do so using the - syntax:
exports.someValue = function(req, res, next) {
//query with mongoose
var query = dbSchemas.SomeValue.find({}).select('name -_id'...
How to read a single character from the user?
...Windows, Linux and OSX: http://code.activestate.com/recipes/134892/
class _Getch:
"""Gets a single character from standard input. Does not echo to the
screen."""
def __init__(self):
try:
self.impl = _GetchWindows()
except ImportError:
self.impl = _Ge...