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Re: Python : map and filter vs for loops The underlying implementation of map and filter are different than loops, even though they accomplish the same thing. Which idiom runs fastest can change from version to version. Right now I think list comprehensions are the fastest. So instead of Code: filter(f, range(2,25)), the list comprehension would be Code: [x for x in range(2,25) if f(x)] and instead of Code: map(cube, range(1, 11)) the list comprehension would be Code: [cube(x) for x in range(1,11)]

"""''.format_map() in Python 2.x"""

keyword arguments with default values can go a long way.

In Python, I think it's more accepted to use duck typing -- asking what an object can do, rather than what it is

it goes against the spirit of Python to worry a lot about what types are passed into methods

It's not an operator as such, so it doesn't really have a name, but it is defined as a "syntactic rule". So it should be called: "the keyword argument unpacking syntax"

# usually a tuple, always an iterable*

# usually a dict, always a mapping*

No need to jump through these loops, See 5.1.1 Using Lists as Stacks

mixin class

Another issue with the __dict__ comparison is what if you have an attribute that you don't want to consider in your definition of equality (say for example a unique object id, or metadata like a time created stamp).

isinstance sucks

Simple Pythonic Rendering Engine.

*name must occur before **name.

keys = sorted(keywords.keys()) for kw in keys: print kw, ":", keywords[kw]

Note that the list of keyword argument names is created by sorting the result of the keywords dictionary’s keys() method before printing its contents; if this is not done, the order in which the arguments are printed is undefined

a if test else b

a well defined mental model of the problem domain

Refining the architecture is part of the "refactor mercilessly" rule

If you've never inherited from a built-in data type, experiment with a small test case in a throw away script. This way you don't mangle your current project and you can be as experimental as you like.

which is just ugly. .format doesn't have those issues. Also in the second example you gave, the .format example is much cleaner looking.

it is advised to somehow mix together (e.g. using exclusive or) the hash values for the components of the object that also play a part in comparison of objects.

If a class does not define a __cmp__() or __eq__() method it should not define a __hash__() operation either

Called when an attribute lookup has not found the attribute in the usual places (i.e. it is not an instance attribute nor is it found in the class tree for self). name is the attribute name. This method should return the (computed) attribute value or raise an AttributeError exception.

Parameters are passed by value

some data types are mutable, but others aren't

If you pass a mutable object into a method, the method gets a reference to that same object and you can mutate it to your heart's delight, but if you rebind the reference in the method, the outer scope will know nothing about it, and after you're done, the outer reference will still point at the original object.

def PreOrder(self): print self.data if self.left: print self.left.PreOrder() if self.right: print self.right.PreOrder()