python-study-notes

reference to do basic operations on iterable objects

get substring	add item	remove item	filter list	map list
split by delimiter	join with delimiter	reverse list	sort list	get max
get min	is item in list	is instance of type	get index of item in list	get indices of item in list
iterate by index	get column in 2d matrix	uppercase string	lowercase string	get unique list items

get substring

letters = "abcdef"
r = letters[0]
print(r)

>> "a"

letters = "abcdef"
r = letters[:-1]
print(r)

>> "abcde"

letters = "abcdef"
r = letters[1:]
print(r)

>> "bcdef"

letters = "abcdef"
r = letters[1:-1]
print(r)

>> "bcde"

items = [1,2,3,4,5]
items.append(6)
print(items)

>> [1, 2, 3, 4, 5, 6]

items = [1,2,3,4,5]
items.insert(2, 'r')
print(items)

>> [1, 2, 'r', 3, 4, 5]

items = [1,2,3,4,5]
del items[0:2]
print(items)

>> [3, 4, 5]

items = [1,2,3,4,5]
items.pop(2)
print(items)

>> [1, 2, 4, 5]

items = [1,2,3,4,5,6,7,8]
r = [i for i in items if i % 2 == 0]
print(r)

>> [2, 4, 6, 8]

items = [1,2,3,4,5,6,7,8]
r = list(filter(lambda i: i % 2 == 0, items))
print(r)

>> [2, 4, 6, 8]

items = [1,2,3,4,5]
r = [i * 2 for i in items]
print(r)

>> [2, 4, 6, 8, 10]

items = [1,2,3,4,5]
r = list(map(lambda i: i * 2, items))
print(r)

>> [2, 4, 6, 8, 10]

letters = 'a b c d e f'
r = letters.split(' ')
print(r)

>> ['a', 'b', 'c', 'd', 'e', 'f']

items = ['a','b','c','d','e']
r = " ".join(items)
print(r)

>> "a b c d e"

items = [1,2,3,4,5]
r = items[::-1]
print(r)

>> [5, 4, 3, 2, 1]

items = [1,2,3,4,5]
items.reverse()
print(items)

>> [5, 4, 3, 2, 1]

items = [2,4,6,1,2,3]
r = sorted(items)
print(r)

>> [1, 2, 2, 3, 4, 6]

items = [2,4,6,1,2,3]
r = sorted(items, reverse=True)
print(r)

>> [6, 4, 3, 2, 2, 1]

items = [1,2,3,6,5,4]
r = max(items)
print(r)

>> 6

items = [6,5,4,1,2,3]
r = min(items)
print(r)

>> 1

items = ['a','b','c','d','e']
print(True) if ('d' in items) else print(False)

>> True

isinstance([1,2,3], list)

>> True

isinstance({'a': 1, 'b': 2}, dict)

>> True

items = ['a','b','c','d','e']
r = items.index('c')
print(r)

>> 2

items = [1,2,3,2,4,6,3,6,9]
r = [i for i in range(len(items)) if items[i] == 3]
print(r)

>> [2, 6]

items = ['a','b','c','d','e']
for i in range(len(items)):
  print(i, end=' ')

>> 0 1 2 3 4

items = [
  [1,2],
  [3,4],
  [5,6],
  ]
r = [i[0] for i in items]
print(r)

>> [1, 3, 5]

letters = "abcde"
r = letters.upper()
print(r)

>> 'ABCDE'

letters = "ABCDE"
r = letters.lower()
print(r)

>> 'abcde'

items = [1,2,2,3,3,3]
r = []
for i in items: i not in r and r.append(i)
print(r)

>> [1, 2, 3]