Basic operations of list and set in python (confusing)

list

1. Create

In [54]: a = list()

In [55]: a
Out[55]: []

Or:

In [56]: a = []

In [57]: a
Out[57]: []

It can also be assigned during direct initialization:

In [58]: a = [1,2,3,'w',(2,3)]

In [59]: a
Out[59]: [1, 2, 3, 'w', (2, 3)]

2. Add elements

  • append() adds an element to the end of the list
In [60]: a.append(5)

In [61]: a
Out[61]: [1, 2, 3, 'w', (2, 3), 5]
  • insert() inserts an element at the specified location in the list
In [62]: a.insert(3,4)

In [63]: a
Out[63]: [1, 2, 3, 4, 'w', (2, 3), 5]
  • extend() to add multiple elements

In [83]: a = [1, 2, 3, 4, 'w', (2, 3), 5]

In [84]: a.extend([1,2,3])

In [85]: a
Out[85]: [1, 2, 3, 4, 'w', (2, 3), 5, 1, 2, 3]

3. Delete element

  • Delete using del (specify location)
In [63]: a
Out[63]: [1, 2, 3, 4, 'w', (2, 3), 5]

In [64]: del a[1]

In [65]: a
Out[65]: [1, 3, 4, 'w', (2, 3), 5]
  • Use pop() to delete
In [65]: a
Out[65]: [1, 3, 4, 'w', (2, 3), 5]

In [66]: val = a.pop()

In [67]: val
Out[67]: 5

In [68]: a
Out[68]: [1, 3, 4, 'w', (2, 3)]

The last value pops up by default, or the value of the specified index

val = a.pop(1)
  • remove() removes elements based on values
In [68]: a
Out[68]: [1, 3, 4, 'w', (2, 3)]

In [69]: a.remove('w')

In [70]: a
Out[70]: [1, 3, 4, (2, 3)]

set

1. Create

a = set()

perhaps

a = {1,2,3,4,'wang',(2,3)}

In this way, the initial value must be assigned, otherwise the dictionary is created

2. Add elements

  • add() to add an item
In [78]: a
Out[78]: {(2, 3), 1, 2, 3, 4, 'wang'}

In [79]: a.add(5)

In [80]: a
Out[80]: {(2, 3), 1, 2, 3, 4, 5, 'wang'}

If the added value is already in the collection, do not operate. (no duplicate elements in collection)

  • update() add multiple
In [86]: a = {(2, 3), 1, 2, 3, 4, 5, 'wang'}

In [87]: a.update([5,6,7])

In [88]: a
Out[88]: {(2, 3), 1, 2, 3, 4, 5, 6, 7, 'wang'}

Note: set has no order

3. Delete element

  • remove() deletes the specified element in the collection, and reports an error if the element does not exist
  • pop() randomly deletes an element in the collection and returns the deleted element (no parameter, distinguished from the list)
  • discard() deletes the specified element in the collection, and does nothing if the element does not exist

Elements cannot be removed by index because the collection is out of order

4. Emptying and combining

In [92]: a
Out[92]: {(2, 3), 1, 2, 3, 4, 5, 6, 7, 'wang'}

In [93]: a.clear()

In [94]: a
Out[94]: set()

Note: for more collection operations, please refer to: The operation and application of collection in python

Tags: Python

Posted on Thu, 04 Jun 2020 11:16:33 -0400 by Riseykins