01-Sequences best practices.md

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Sequences Best Practices (list, tuples and dictionaries)

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Multi line constructs

• ex - good:

long_list = [
    1,2,3
    4,5,6
    ]

• this also works:

long_list = [
    1,2,3
    4,5,6
]

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Sequences as Truthy and Falsy values

• Non empty sequence = True
• Empty = False ( set() is False)
• bad: if len(my_list) > 0 :
• good: if my_list ... if my_list has items in it it will evaluate to True and will run
• if you want to run code if a list is empty do something like this... if not my_list

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List comprehension and when to use it

• use list comprehension when it makes your code easier to read
• syntax: [expression for item in iterable]
• example:

pizza_letters = [letter.upper() for letter in "pizza"]
pizza_letters = [letter * 2 for letter in "pizza"]
pizza_letters = [letter for letter in "pizza"]
nums = [random.randint(1, 15) for i in range(250)]
theitems = [myfunction(var) for var in iterable]
the_nums = [i for i in range(50) if i % 2 == 0]

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Dictionary comprehension

• syntax: ```{key: value for elem in iterable }
• example:

my_dict = {i: i*2 for i in range(2, 8)}
my_dict = {item: round(price*1.2,3) for (item, price) in old_prices.items() }