Writing idiomatic python pdf

As I said, there are tons and tons of cute little tricks that you can do with dictionaries. List comprehensions are neat little constructs that will shorten your lines of code considerably.

I find list comprehensions to be very useful for both file parsing and for simple math. Consider a file containing data and comments:. For simple math, suppose you need to calculate the average and stddev of some numbers. Just use a list comprehension:. Oh, and one rule of thumb: if your list comprehension is longer than one line, change it to a for loop; it will be easier to read, and easier to understand.

This is actually quite easy, if you make the Binner class look like a list by adding two special functions:. The second case involves a bit more implicit magic. Here, Python figures out that Binner can act like a list and simply calls the right functions to retrieve the information.

In turn, this can make your code look much simpler and feel much cleaner. Mediating between these options is mostly a matter of experience. This just means that Python agrees to respect anything that supports a particular set of methods as if it were an iterator.

I use this if I just want to get the first value or two from an iterator. For example, suppose you had the following class:. Generators are a Python implementation of coroutines. To do the equivalent with an iterator would require a class, so that the object instance can hold the variables:. It is also much easier to write routines like enumerate as a generator than as an iterator:. One of the most underused keywords in Python is assert.

Assert is pretty simple: it takes a boolean, and if the boolean evaluates to False, it fails by raising an AssertionError exception. Want to make sure that a particular return value is not None? For example,. If you need to raise an exception in production code, see below. Use of common Python idioms — both in your python code and for your new types — leads to short, sweet programs. How slow is Python really? Or how fast is your language? Although it wasn't my intent Python programers have told me this page has Cheat Sheet: Writing Python compatible code Python The futurize and python-modernize tools do not currently offer an option to do this automatically.

If you are writing code for a new project or new codebase you can Python programming language - Wikipedia Python is a widely used high-level programming language used for general-purpose programming created by Guido van Rossum and first released in Which is the preferred way to concatenate a string in Python?

This is because it's readable and fast. They are also just as fast which one you choose is