sloria

f = open('file.txt', 'w')
f.write('hi')
f.close()

# Better
with open('file.txt', 'w') as f:
    f.write('hi')   

with pytest.raises(ValueError):
    int('hi')

sloria

if self.flags & 0b1000:  # Am I visible?
    ...

# Better
...
@property
def is_visible(self):
    return self.flags & 0b1000

if self.is_visible:

sloria

# Bad
if type(entry) is Film:
    responsible = entry.producer
else:
    responsible = entry.author

# Shouldn't use type() or isinstance() in conditional --> smelly

# Better
class Film:

sloria

class ParagraphEditor:
    ...
    def highlight(self, rectangle):
        self.reverse(rectangle)

# Better
class ParagraphEditor:
    ...
    highlight = reverse  # More readable, more composable

sloria

_DEFAULT_PORT = 1234

class SomeProtocol:
    ...
    def __enter__(self):
        self._client = socket()
        self._client.connect(
            (self.host,
            self.port or _DEFAULT_PORT)
        )

sloria

class Point:
    def __init__(self, x, y):
        self.x, self.y = x, y

# Sometimes need more flexibility --> use properties

class Point:
    def __init__(self, x, y):
        self._x, self._y = x, y

sloria

# Bad
# Can't change type of collection
#     e.g. can't change employees from a list to a set
class Department:
    def __init__(self, *employees):
        self.employees = employees

for employee in department.employees:
    ...
    

sloria

# Meh
class Rectangle:
    def bottom_right(self):
        return Point(self.left + self.width,
                    self.top + self.height)

# Better to use temporary variables for readability
class Rectangle:
    ...
    def bottom_right(self):

sloria

item in a_set
item not in a_set

# a_set <= other
a_set.is_subset(other)

# a_set | other
a_set.union(other)

# a_set & other

sloria

obj == obj2
obj1 is obj2

class Book:
    ...
    def __eq__(self, other):
        if not isinstance(other, self.__class__):
            return NotImplemented
        return (self.author == other.author and 
                self.title == other.title)