13. Built-in Functions¶

13.1 Numeric¶

x = '47'
y = int(x)

int is a constructor for the type int.
similarly, there is a float constructor
abs returns absolute value of a number. Works on floats and ints.
divmod returns both quotient and remainder in a tuple.
complex is a type constuctor for complex numbers. Example: y = x + 73j or y = complex(x, 73)
Complete set of built-in functions are in the [documentation].(https://docs.python.org/3/library/functions.html)

13.2 String¶

s = 'Hello, World.'
print(repr(s))

prints the string itself.
repr is a method that most classes have.

class bunny:
    def __init__(self, n):
        self._n = n
    def __repr__(self):
        return f'repr: the number of bunnies is {self._n}'
    def __str__(self):
        return f'str: the number of bunnies is {self._n}'
<>
x = bunny(47)
print(x) # defaults to the str version
print(repr(x)) # if there's no str method, it prints the repr method

13.3 Container¶

x = (1, 2, 3, 4, 5)

y = len(x) returns length
y = reversed(x) provides an iterator with the reversed object
y = list(reversed(x)) provides a reversed list
y = sum(x) returns sum
y = sum(x, 10) returns sum(x) + 10
min, max
any returns True if any of them are True. Similarly, all.
z = zip(x, y) returns an iterator. for a, b in zip(x, y):
enumerate returns index and value. for i, a in enumerate(x):

13.4 Object¶

x = 42
y = type(x)
print(x)
print(y)

type operates on an object and returns the class.
to check in code, y = isinstance(x, int)
y = id(x) returns a unique number for an object. Same objects have the same id.

12. File I/O 14. Modules