To summarize the contents of other (already good!) answers, isinstance caters for inheritance (an instance of a derived class is an instance of a base class, too), while checking for equality of type does not (it demands identity of types and rejects instances of subtypes, AKA subclasses). Normally, in Python, you want your code to … Read more
You can totally do that. It’s just an ordering issue: [f(x) if x is not None else ” for x in xs] In general, [f(x) if condition else g(x) for x in sequence] And, for list comprehensions with if conditions only, [f(x) for x in sequence if condition] Note that this actually uses a different … Read more
Linked to, but not explicitly mentioned here, is exactly when __all__ is used. It is a list of strings defining what symbols in a module will be exported when from <module> import * is used on the module. For example, the following code in a foo.py explicitly exports the symbols bar and baz: __all__ = … Read more
Getting the name of the file without the extension: import os print(os.path.splitext(“/path/to/some/file.txt”)[0]) Prints: /path/to/some/file Documentation for os.path.splitext. Important Note: If the filename has multiple dots, only the extension after the last one is removed. For example: import os print(os.path.splitext(“/path/to/some/file.txt.zip.asc”)[0]) Prints: /path/to/some/file.txt.zip See other answers below if you need to handle that case.
Use a dict comprehension (Python 2.7 and later): {key: value for (key, value) in iterable} Alternatively for simpler cases or earlier version of Python, use the dict constructor, e.g.: pairs = [(‘a’, 1), (‘b’, 2)] dict(pairs) #=> {‘a’: 1, ‘b’: 2} dict([(k, v+1) for k, v in pairs]) #=> {‘a’: 2, ‘b’: 3} Given separate … Read more
NOTE: For Python 3.3+, see The Aelfinn’s answer below. Use the –python (or short -p) option when creating a virtualenv instance to specify the Python executable you want to use, e.g.: virtualenv –python=”/usr/bin/python2.6″ “/path/to/new/virtualenv/”
Your data is not valid JSON format. You have [] when you should have {} for the “masks” and “parameters” elements: [] are for JSON arrays, which are called list in Python {} are for JSON objects, which are called dict in Python Here’s how your JSON file should look: { “maps”: [ { “id”: … Read more
In Python 3, print can take an optional flush argument: print(“Hello, World!”, flush=True) In Python 2, after calling print, do: import sys sys.stdout.flush() By default, print prints to sys.stdout (see the documentation for more about file objects).
The syntax is the * and **. The names *args and **kwargs are only by convention but there’s no hard requirement to use them. You would use *args when you’re not sure how many arguments might be passed to your function, i.e. it allows you pass an arbitrary number of arguments to your function. For … Read more
The simplest way in Python: import time start_time = time.time() main() print(“— %s seconds —” % (time.time() – start_time)) This assumes that your program takes at least a tenth of second to run. Prints: — 0.764891862869 seconds —