Effective Python 01 - 05

I am reading the book Effective Python: 90 Specific Ways to Write Better Python (click here to see it) and will write 18 blog entries, 1 per week, each covering 5 ways. To keep everything bite-sized (no pun intended), I will write a synopsis for each way; many things will be left out, but I will try to capture the most important ones.

I will use Python 3 for the examples.

Item #01: Know which version of Python you are using.

This is achieved with the command $ python --version or at run-time:

    import sys

    print(sys.version)

Item #02: Follow the most recent PEP style guide.

It is extensive. Click here to learn more. Memorize it! A few highlights are: spaces over tabs, 4 spaces of indentation, def this_is_my_function(self):, class ThisIsMyClass:, THIS_IS_MY_GLOBAL_VARIABLE = foo, etc.

Item #03: Know the differences between bytes and str.

Python has two types that represent sequences of character data: bytes and str.

Instances of bytes contain raw, unsigned, 8-bit values that are often displayed in the ASCII encoding:

    x = b'h\x65llo'

    print(list(x), x, type(x))

    >>>

    [104, 101, 108, 108, 111] b'hello' <class, 'bytes'>

Instances of str contain Unicode code points that represent textual characters from human languages.

Item #04: Prefer interpolated f-strings over C-style format strings and str.format.

Let name = 'John Doe'. Prefer to do this: f'My name is {name}.' over 'My name is %s.' % name and 'My name is {0}.'.format(name).

This is a general rule. The documentation says that the logging library is optimized to use C-style strings; this could make a difference at large scales.

Item #05: Write helper functions instead of complex expressions.

Suppose that you have a Chess class that has a complicated function def play_best_move(self):. It is better to rewrite it as follows (to give a simple example):

    def play_best_move(self):

        legal_moves = self.get_legal_moves()

        best_move = self.rank_moves_inc(legal_moves)[-1]

        self.play_move(best_move)

Note that these are reusable functions. For example:

    def play_worst_move(self):

        legal_moves = self.get_legal_moves()

        worst_move = self.rank_moves_inc(legal_moves)[0]

        self.play_move(worst_move)