Building with built-ins
Writing Efficient Python Code
Logan Thomas
Scientific Software Technical Trainer, Enthought
The Python Standard Library
- Python 3.6 Standard Library
- Part of every standard Python installation
- Built-in types
list,tuple,set,dict, and others
- Built-in functions
print(),len(),range(),round(),enumerate(),map(),zip(), and others
- Built-in modules
os,sys,itertools,collections,math, and others
Built-in function: range()
Explicitly typing a list of numbers
nums = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Using range() to create the same list
# range(start,stop)
nums = range(0,11)
nums_list = list(nums)
print(nums_list)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
# range(stop)
nums = range(11)
nums_list = list(nums)
print(nums_list)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Built-in function: range()
Using range() with a step value
even_nums = range(2, 11, 2)
even_nums_list = list(even_nums)
print(even_nums_list)
[2, 4, 6, 8, 10]
Built-in function: enumerate()
Creates an indexed list of objects
letters = ['a', 'b', 'c', 'd' ]
indexed_letters = enumerate(letters)
indexed_letters_list = list(indexed_letters)
print(indexed_letters_list)
[(0, 'a'), (1, 'b'), (2, 'c'), (3, 'd')]
Built-in function: enumerate()
Can specify a start value
letters = ['a', 'b', 'c', 'd' ]
indexed_letters2 = enumerate(letters, start=5)
indexed_letters2_list = list(indexed_letters2)
print(indexed_letters2_list)
[(5, 'a'), (6, 'b'), (7, 'c'), (8, 'd')]
Built-in function: map()
Applies a function over an object
nums = [1.5, 2.3, 3.4, 4.6, 5.0]
rnd_nums = map(round, nums)
print(list(rnd_nums))
[2, 2, 3, 5, 5]
Built-in function: map()
map() with lambda (anonymous function)
nums = [1, 2, 3, 4, 5]
sqrd_nums = map(lambda x: x ** 2, nums)
print(list(sqrd_nums))
[1, 4, 9, 16, 25]
Let's start building with built-ins!
Writing Efficient Python Code
