notes

Python Tips

Getting Help

1. List methods

    dir(obj)
   

2. Print help

    help(obj)
   

List comprehension

>>> [ord(x) for x in 'spaam']                # List of character ordinals
[115, 112, 97, 97, 109]
>>> {ord(x) for x in 'spaam'}                # Sets remove duplicates
{112, 97, 115, 109}
>>> {x: ord(x) for x in 'spaam'}             # Dictionary keys are unique
{'p': 112, 'a': 97, 's': 115, 'm': 109}
>>> (ord(x) for x in 'spaam')                # Generator of values
<generator object <genexpr> at 0x000000000254DAB0>

Difference Between bytes and str

1. 1 byte != 1 character in string, it all depends on encoding
2. What every SD should know about Unicode

3. open function by uses os default encoding when tries to open a file (most of the time it’s utf-8), so if you want to read a binary file use:

    with open('data.bin', 'rb') as f:
        data = f.read()
   

Iteration over the list

1. prefer to use for x in arr instead of for i in range(arr)

2. if you need to get index and value at the same time use enumerate

    flavor_list = ['vanilla', 'chocolate', 'pecan', 'strawberry']
   
    for i, flavor in enumerate(flavor_list, 1):
        print(f'{i}: {flavor}')
   
    >>>
    1: vanilla
    2: chocolate
    3: pecan
    4: strawberry
   

Use zip to process iterators in parallel

names = ['Cecilia', 'Lise', 'Marie']
counts = [len(n) for n in names]

for name, count in zip(names, counts):
    print(name, count)

Use warlus to assign and evaluate variable

if count := fresh_fruit.get('lemon', 0):
    make_lemonade(count)
else:
    out_of_stock()

Use catch-all while unpacking

# get the top from a list
car_ages = [0, 9, 4, 8, 7, 20, 19, 1, 6, 15]
car_ages_descending = sorted(car_ages, reverse=True)
oldest, second_oldest, *others = car_ages_descending

# header and body
it = generate_csv()
header, *rows = it