What are the python sequence types?

What are the sequence types in python? What is a sequence type in Python? Learn more about it in this article.

Sequence: character, list, tuple

All sequences support iteration

Sequence Represents an ordered collection of objects whose index is a non-negative integer

Characters and tuples belong to immutable sequences, and lists are mutable

1)Characters

String literal: Put the text in single quotes, double quotes or triple quotes;

    '    ''    '''
        >>> str1 = ' hello, fanison '
        >>> type(str1)
        str

If you want to use unicode encoding, use the character u before the character to identify it

        >>> str2 = u'你好，fanison'
        >>> type(str2)
        unicode

Documentation string: If the first statement of a module, class or function is one character, the string becomes the documentation string and can be referenced using the __doc__ attribute;

Example:

            >>> def printName():
                    "the function is print hello"
                    print 'hello'
            >>> printName.__doc__

operator:

# S [i] Return to a sequence element I

slicing computing s [i: j] Return to one Slicing

Extended slicing operator s[i:j:stride]

Example:

            >>> str3 = 'hello,fanison'
            >>> str2[0:]
            'hello,fanison'      返回所有元素
            >>> str2[0:7]
            'hello,f'            返回索引7之前的所有元素
            >>> str2[0:7:2]
            'hlof'               返回从索引0到6内步径为2的元素，即隔一个取一个
            >>> str2[7:0:-2]        
            'a,le'               从索引7处倒着隔一个取一个取到索引1处
            >>> str2[-4:-1]
            'iso'                从索引-4处取到-2处       
            >>> str2[-4::-1]
            'inaf,olleh'         从-4处到开始处倒着取

Note:

Step If it is positive, it means that the index is taken from small to large i < j

The step path is negative, it means that it is taken backward, and the index is from large to small i > j

Supported Operations:

Indexing, slicing, min(), max(), len(), etc.

       

len(s)               The number of elements in s

min (s) s minimum value

Max (s) s) The maximum value of

## Support method:

S.index (SUB [,start [,end]])           Find the position where the specified string sub first appears

S.upper()                                     Convert a string to uppercase form

S.lower()                                                              one String into a lowercase form

# S.Join (T) uses S as a string in the separatist connection sequence T

 >>> l1 = list(str1)
>>> l1
['h', 'e', 'l', 'l', 'o', ',', 'f', 'a', 'n', 'i', 's', 'o', 'n']
>>> ''.join(l1)
'hello,fanison'             使用空字符作为分隔符连接列表l1
S.replace(old, new[, count])             替换一个字符串
>>> str1.replace('fan','FAN')
'hello,FANison'

Note:

## Use help () to get Its help

>>> help(str.join)

           

2) List

List: Container Type

                                                                                                                                                                                                            . Modify

to modify the specified index element, modify the specified shard, delete the statement, the built -in method

##

         >>> list1 = [ 1,2,3,'x','n' ]
         >>> list1[1]=56
         >>> print list1
         [1, 56, 3, 'x', 'n']
         >>> list1[1:3]=[]              会删除索引1到索引3之前的元素
         >>> print list1
         [1, 'x', 'n']   
         >>> del(list1[1])              使用del函数删除list索引为1的元素
         >>> print list1
         [1, 'n']

Note:

## Because support the original modification of the original place , Will not change the memory location, you can use ID () to view its location change

Built

##               L.append(object)               Append a new element to the end of L                                                                           ’s . Add a merged list (the contents of the second list will be appended to the end as a single element)

      >>> l1 = [ 1,2,3 ]
                        >>> l2 = [ 'x','y','z']
                        >>> l1.append(l2)
                        >>> l1
                        [1, 2, 3, ['x', 'y', 'z']]          使用append方法会以其原有存在形式追加
                        >>> l1 = [ 1,2,3 ]
                        >>> l1.extend(l2)
                        >>> l1
                        [1, 2, 3, 'x', 'y', 'z']            注意两种增加的区别

L.pop ([Index]) Return the element index and remove it from the list. The element that is key

                        >>> l1 = [ 'x',2,'abc',16,75 ]
                        >>> l1.pop(2)                       pop方法是按索引移除
                        'abc'
                        >>> l1
                        ['x', 2, 16, 75]
                        >>> l1.remove(16)                   remove方法是按值移除
                        >>> l1
                        ['x', 2, 75]

                                                                                                                                                        to ’ s ’ s ’ s ’ s to ’ t               ’ ’ ’ ’ s ‐ to ‐ ‐ ‐‐ ‐‐ ‐‐n-key, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​  

L.insert(index, object) 在索引index处插入值

                        >>> l1.insert(1,'abc')
                        >>> l1
                        ['x', 'abc', 2, 75]

L.sort() 排序

L.reverse() 逆序

                        >>> l1.sort()
                        [2, 75, 'abc', 'x']
                        >>> l1.reverse()
                        ['x', 'abc', 75, 2]

l1 + l2: 合并两个列表，返回一个新的列表；不会修改原列表；

                        >>> l1 = [ 1,2,3]
                        >>> l2 = [ 'x','y','z']
                        >>> l1 + l2
                        [1, 2, 3, 'x', 'y', 'z']

l1 * N: 把l1重复N次，返回一个新列表;

                        >>> l1 * 3
                        [1, 2, 3, 1, 2, 3, 1, 2, 3]         使用id()查看是否生成新列表

成员关系判断字符：

in 用法： item in container

not in item not in container

                            >>> l1 = [ 'x','y',3 ]
                            >>> 'y' in l1
                            True
                            >>> 'x' not in l1
                            False

列表解析：[]

列表复制方式：

浅复制:两者指向同一内存对象

                    >>> l1 = [ 1,2,3,4 ]
                    >>> l2 = l1
                    >>> id(l1) == id(l1)
                    True                            可以看出两者内存地址相同
                    >>> l1.append('x')
                    >>> print l1
                    [ 1,2,3,4,'x' ]
                    >>> print l2
                     [ 1,2,3,4,'x' ]

深复制：两者指向不同内存对象

1)导入copy模块，使用deepcoop方法

                     >>> import copy
                     >>> l3 = copy.deepcopy(l1)
                     >>> id(l3) == id(l1)
                     False                          地址不同

2)复制列表的所有元素，生成一个新列表

                    >>> l4 = l1[:]              
                    >>> print l4
                    [ 1,2,3,4,'x' ]
                    >>> l1.append(6)
                    >>> print l1
                    [ 1,2,3,4,'x',6 ]               l1改变
                    >>> print l4
                    [ 1,2,3,4,'x' ]                 l4不变

3)元组

表达式符号：()

容器类型

任意对象的有序集合，通过索引访问其中的元素，不可变对象，长度固定，异构，嵌套

常见操作：

                    >>> t1 = ( 1,2,3,'xyz','abc')
                    >>> type(t1)
                    tuple
                    >>> len(t1)
                    5
                    >>> t2 = ()                             定义一个空元组
                    >>> t3 = ( , )
                    SyntaxError: invalid syntax             报错：使用逗号分隔的条件是最少要有一个元素

(1,)

                    >>> t1[:]
                    ( 1,2,3,'xyz','abc' )
                    >>> t1[1:]
                    (2, 3, 'xyz', 'abc')

(1,2)

                    >>> t1[1:4]
                    (2, 3, 'xyz')
                    >>> t4 = 'x',1,'yz',45,[2,4,6]              注意!!!这样也可以生成元组
                    >>> t4  
                    ('x', 1, 'yz', 45, [2, 4, 6])

t1 + t4: 合并两个元组，返回一个新的元组；不会修改原元组；

                    >>> t1 + t4
                    (1, 2, 3, 'xyz', 'abc', 'x', 1, 'yz', 45, [2, 4, 6])

t1 * N: 把l1重复N次，返回一个新元组;

                    >>> t1 * 3
                    (1, 2, 3, 'xyz', 'abc', 1, 2, 3, 'xyz', 'abc', 1, 2, 3, 'xyz', 'abc')

成员关系判断

in

not in

注意：

虽然元组本身不可变，但如果元组内嵌套了可变类型的元素，那么此类元素的修改不会返回新元组；

例：

                    >>> t4 = ('x', 1, 'yz', 45, [2, 4, 6])
                    >>> id(t4)
                    44058448
                    >>> t4[4]                           
                    [2, 4, 6]
                    >>> t4[4].pop()                     弹出列表内一个元素
                    6
                    >>> print t4[4]
                    [2, 4]
                    >>> print t4
                    ('x', 1, 'yz', 45, [2, 4]) 
                    >>> id(t4)
                    44058448                            由此可见，对元组内列表内的修改也会使元组发生改变，没有返回新元组

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