[Python] #3 Python Structed Data

This is a self note while taking the online course from: LinkedIn Learning: Learning Python by Joe Marini LinkedIn Learning: Python Essential Training by Bill Weinman

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1. List, Tuple

• Lists are mutable, but tuples are immutable.

• using join function when printing elements:

list_a = ['a', 'b', 'c']
print(', '.join(list_a))

(Result)

a, b, c

2. Dictionary

• Initializing dictionaries:

# match each data in pairs in brackets {}
numbers = {'1': 'one', '2': 'two', '3': 'three'}

# use dict() function
nums = dict(one='1', two='2', three='3')

• Accessing keys and values, or both:

nums = dict(one='1', two='2', three='3')

# key and value pairs
for k, v in nums.items():
    print(f'({k}, {v})')
print()

# only keys
for k in nums.keys():
    print(k)
print()

# only values
for v in nums.values():
    print(v)
print()

# access to a value
print(nums['one'])
nums['one'] = '1one1'
print(nums['one'])

(Result)

(one, 1)
(two, 2)
(three, 3)

one
two
three

1
2
3

1
1one1

3. Set

• Set does not allow duplicate, but mutable
• Strings can be stored as sets:

a = set("My name is David Oh")
print(a)
print('\n\nsorted:')
print(sorted(a))

(Result)

{' ', 'v', 'y', 'd', 'e', 'D', 'n', 'O', 'm', 'h', 'M', 'a', 's', 'i'}

sorted:
[' ', 'D', 'M', 'O', 'a', 'd', 'e', 'h', 'i', 'm', 'n', 's', 'v', 'y']

• Set operators: -, &,

  , ^(xor)

4. List Comprehension

seq = range(11)
print(list(seq))
print()

# list comprehension
seq2 = [x*2 for x in seq]
print(seq2)

seq3 = [x for x in seq if x % 3 != 0]
print(seq3)
print()

# list of tuples
seq4 = [(x, x**2) for x in seq]
print(seq4)
print()

# dictionaries
seq5 = {x: x**2 for x in seq}
print(seq5)
print()

# sets
seq6 = {x for x in 'South Korea' if x in 'North Korea'}
print(seq6)

(Result)

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

[0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20]
[1, 2, 4, 5, 7, 8, 10]

[(0, 0), (1, 1), (2, 4), (3, 9), (4, 16), (5, 25), (6, 36), (7, 49), (8, 64), (9, 81), (10, 100)]

{0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81, 10: 100}

{'t', 'K', ' ', 'a', 'e', 'h', 'r', 'o'}