Python sequence is the most basic data structure. Each element in the sequence is assigned a number - its position, or index, the first index is 0, the second index is 1, and so on.
Python has a built-in type 6 sequences, but the most common are lists and tuples.
A sequence of operations can be carried out, including indexing, slicing, add, multiply, check members.
Further, Python already has built-in methods for sequence length, the maximum and minimum element. You may like this Python course
List
Python list is one of the most common types of data. It appears as a comma-separated values in square brackets.
Create a list, as long as the comma-separated data items using different brackets can be as follows:
>>> list1 = [ 'physics', 'chemistry', 1997, 2000]
>>> list2 = [1, 2, 3, 4, 5]
>>> list3 = [ "a", "b", "c", "d"]
>>>
Like string indices, list indices start at 0. The list can be intercepted, combinations and the like.
Access list values
The index is used to access the values in the list, as follows:
>>> list1 = [ 'physics', 'chemistry', 1997, 2000]
>>> list2 = [1, 2, 3, 4, 5]
>>> print(list1[0])
physics
>>> print(list2[0])
1
>>> print(list1[1:3])
['chemistry', 1997]
>>> print(list2[1:3])
[2, 3]
>>>
update list
You can modify or update data items in the list, you can also add a list item using append() method, as follows:
>>> list1 = [ 'physics', 'chemistry', 1997, 2000]
>>> list1[2] = 2010
>>> list1
['physics', 'chemistry', 2010, 2000]
>>>
>>> list1.append("Tango")
Delete list elements
You can use the del statement to delete the list of elements, the following examples:
>>> list1 = [ 'physics', 'chemistry', 1997, 2000]
>>> list1
['physics', 'chemistry', 1997, 2000]
>>> del list1[1]
>>> list1
['physics', 1997, 2000]
>>>
Python script operator list
Similar lists of + and * operators string. + Number combination for the list, the list for repeatedly asterisk.
As follows:
| Python expressions | result | Description |
|---|---|---|
| len ([1, 2, 3]) | 3 | length |
| [1, 2, 3] + [4, 5, 6] | [1, 2, 3, 4, 5, 6] | composition |
| [ 'Hi!'] * 4 | [ 'Hi!', 'Hi!', 'Hi!', 'Hi!'] | Repeat |
| 3 in [1, 2, 3] | True | element exists in the list |
| for x in [1, 2, 3]: print x, | 1 2 3 | iteration |
Python interception list
Python list operation type string taken as follows:
L = [ 'spam', 'Spam', 'SPAM!']
operating:
| Python expressions | result | Description |
|---|---|---|
| L [2] | 'SPAM!' | Third element in the list is read |
| L [-2] | 'Spam' | penultimate read list element |
| L [1:] | [ 'Spam', '! SPAM'] | taken from the second list element start |
Python list of functions & methods
Python includes the following functions:
| No. | function |
|---|---|
| 1 | cmp(list1, list2) Compare the two lists of elements |
| 2 | len(list) The number of list elements |
| 3 | max(list) Returns a list of elements of the maximum |
| 4 | min(list) Returns a list of elements of the minimum |
| 5 | list(seq) Convert a list of tuples |
Python includes the following methods:
| No. | Methods |
|---|---|
| 1 | list.append(obj) Add new object at the end of the list |
| 2 | list.count(obj) The number of times an element statistics appear in the list |
| 3 | list.extend(seq) A plurality of values in another sequence added at the end of the list of one-time (with a new list of the original extended list) |
| 4 | list.index(obj) A value index to find the location of the first match from the list |
| 5 | list.insert(index, obj) Inserting objects list |
| 6 | list.pop(obj = list [-1]) Removing one element in the list (default to the last element), and returns the value of the element |
| 7 | list.remove(obj) Remove the list a value of the first match |
| 8 | list.reverse() Reverse elements in the list |
| 9 | list.sort([func]) The original list is sorted |
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