Python Common data structures

0. Dictionary initialization

D = {' A ': 1, ' B ': 2}

or d={}

D[' a '] = 1

D[' B '] = 2

is not like JSON format data, syntax and JavaScript are very similar

1. Variable Accept sequence decomposition:

p = (3.14,8.23)

X, y = P

Print (x, y)

3.14,8.23

2. Collections.deque fixed length queue.

>>> from collections Import deque

>>> p = deque (MaxLen = 2)

>>> p.append (3.14)

>>> P.append (8.23)

>>> P

Deque ([3.14, 8.23], maxlen=2)

3. HEAPQ maximum minimum value.

>>> Import HEAPQ

>>> p = [3.14,8.23,7.10]

>>> Heapq.nlargest (1,p)

[8.23]

>>> Heapq.nsmallest (1,p)

[3.14]

5. Find two dictionaries of the same key and same item

>>> from collections Import Ordereddict

>>> d = {}

>>> d[' a '] = 1

>>> d[' c '] = 3

>>> d[' b '] = 2

>>> dd = {}

>>> dd[' a '] = 3

>>> dd[' e '] = 5

>>> dd[' b '] = 2

>>> D.keys () & Dd.keys ()

{' A ', ' B '}

>>> d.items () & Dd.items ()

{(' B ', 2)}

6 Remove array or dictionary value duplicate element set

>>> D ={1,1,2,2,3,3,4,5}

>>> Set (d)

{1, 2, 3, 4, 5}

7 Intercepting array elements

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

>>> D[2:4]

[2, 2]

>>> D[2:5]

[2, 2, 3]

8 statistics element Occurrences Counter.most_common.

>>> d = [1,1,1,2,2,4,5]

>>> from collections Import Counter

>>> master = Counter (d). Most_common (2)

>>> Print (Master)

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

4. Collections. Ordereddict ordered Dictionary

>>> from collections Import Ordereddict

>>> d = ordereddict ()

>>> d[' a '] = 1

>>> d[' c '] = 3

>>> d[' b '] = 2

>>> Print (d)

Ordereddict (' A ', 1), (' C ', 3), (' B ', 2)])

9. Array sorting Operator.itemgetter

>>> from operator Import Itemgetter

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

>>> Sorted (d)

[1, 2, 3, 4, 5]

10. Sort Dictionary

>>> from operator Import Itemgetter

>>> p = [{' X ': ' 3 ', ' Y ': ' 3 '},{' x ': ' 4 ', ' Y ': ' 4 '},{' x ': ' 2 ', ' Y ': ' 2 '},{' x ': ' 1 ', ' y ': ' 1 '}]

>>> P.sort (Key=itemgetter (' x '))

>>> Print (P)

[{' X ': ' 1 ', ' y ': ' 1 '}, {' X ': ' 2 ', ' Y ': ' 2 '}, {' X ': ' 3 ', ' Y ': ' 3 '}, {' X ': ' 4 ', ' Y ': ' 4 '}]

One-to-one lambda expressions

>>> p = [{' X ': ' 3 ', ' Y ': ' 3 '},{' x ': ' 4 ', ' Y ': ' 4 '},{' x ': ' 2 ', ' Y ': ' 2 '},{' x ': ' 1 ', ' y ': ' 1 '}]

>>> plamb = [n[' x '] > ' 2 ' for n in P]

>>> Print (PLAMB)

[True, True, False, false]

The compress is used in conjunction with 11 items.

>>> from Itertools Import compress

>>> list (compress (P,PLAMB))

[{' X ': ' 3 ', ' Y ': ' 3 '}, {' X ': ' 4 ', ' Y ': ' 4 '}]

13. Logically merging objects

>>> p = {' x ': 1, ' Y ': 2}

>>> P2 = {' Y ': 3, ' Z ': 4}

>>> from collections Import Chainmap

>>> C = Chainmap (P,P2)

>>> Print (c)

Chainmap ({' X ': 1, ' Y ': 2}, {' Y ': 3, ' Z ': 4})

>>> list (C.keys ())

[' x ', ' z ', ' y ']

Python Common data structures