How to parse a RFC 2822 date/time into a Python datetime?
The problem is that parsedate will ignore the offset. Do this instead: from email.utils import parsedate_tz print parsedate_tz(‘Fri, 15 May 2009 17:58:28 +0700’)
python-2.5
How to: Macports select python
Use osx$ port select –list python to list your available Python installations. Then use the “–set” option to “port select” to set the port you wish to use. osx$ sudo port select –set python python27
Read data from CSV file and transform from string to correct data-type, including a list-of-integer column
As the docs explain, the CSV reader doesn’t perform automatic data conversion. You have the QUOTE_NONNUMERIC format option, but that would only convert all non-quoted fields into floats. This is a very similar behaviour to other csv readers. I don’t believe Python’s csv module would be of any help for this case at all. As … Read more
Sort nested dictionary by value, and remainder by another value, in Python
Use the key argument for sorted(). It lets you specify a function that, given the actual item being sorted, returns a value that should be sorted by. If this value is a tuple, then it sorts like tuples sort – by the first value, and then by the second value. sorted(your_list, key=lambda x: (your_dict[x][‘downloads’], your_dict[x][‘date’]))
How does Python’s “super” do the right thing?
Change your code to this and I think it’ll explain things (presumably super is looking at where, say, B is in the __mro__?): class A(object): def __init__(self): print “A init” print self.__class__.__mro__ class B(A): def __init__(self): print “B init” print self.__class__.__mro__ super(B, self).__init__() class C(A): def __init__(self): print “C init” print self.__class__.__mro__ super(C, self).__init__() class … Read more
Subclassing int in Python
int is immutable so you can’t modify it after it is created, use __new__ instead class TestClass(int): def __new__(cls, *args, **kwargs): return super(TestClass, cls).__new__(cls, 5) print TestClass()
How to properly use python’s isinstance() to check if a variable is a number?
In Python 2, you can use the types module: >>> import types >>> var = 1 >>> NumberTypes = (types.IntType, types.LongType, types.FloatType, types.ComplexType) >>> isinstance(var, NumberTypes) True Note the use of a tuple to test against multiple types. Under the hood, IntType is just an alias for int, etc.: >>> isinstance(var, (int, long, float, complex)) … Read more
Tell if Python is in interactive mode
__main__.__file__ doesn’t exist in the interactive interpreter: import __main__ as main print hasattr(main, ‘__file__’) This also goes for code run via python -c, but not python -m.
Check if input is a list/tuple of strings or a single string
You can check if a variable is a string or unicode string with Python 3: isinstance(some_object, str) Python 2: isinstance(some_object, basestring) This will return True for both strings and unicode strings As you are using python 2.5, you could do something like this: if isinstance(some_object, basestring): … elif all(isinstance(item, basestring) for item in some_object): # … Read more
How can I obtain the image size using a standard Python class (without using an external library)?
Here’s a Python 3 script that returns a tuple containing an image height and width for .png, .gif and .jpeg without using any external libraries (i.e., what Kurt McKee referenced). It should be relatively easy to transfer it to Python 2. import struct import imghdr def get_image_size(fname): ”’Determine the image type of fhandle and return its … Read more