Array types in various programming languages is the basic structure of the array, the inventory herein to Pythonvarious "array" type of implementation.
listtuplearray.arraystrbytesbytearray
In fact, the above said as an array type is not accurate. Here the array as a broad concept, ie the list, the sequence, as are an array ofarray-likedata types to understand.
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Note This article All code is in the Python3.7running in _
0x00 variable dynamic list of list
listIt should be Pythonan array of the most commonly used type. It is characterized by variable, dynamically expansion, may store Pythonall the object without specifying the type of storage element during use.
Very easy to use
>>> arr = ["one","two","three"]
>>> arr[0]
'one'
# 动态扩容
>>> arr.append(4)
>>> arr
['one', 'two', 'three', 4]
# 删除一个元素
>>> del arr[2]
>>> arr
['one', 'two', 4]
0x01 immutable tuple
tupleThe operation listis similar. It is characterized immutable, not expansion, may store Pythonall the object without specifying the type of storage element during use.
>>> t = 'one','two',3
>>> t
('one', 'two', 3)
>>> t.append(4)
AttributeError: 'tuple' object has no attribute 'append'
>>> del t[0]
TypeError: 'tuple' object doesn't support item deletion
tupleYou can use +the operator, the operator will create a new tupleobject is used to store data.
>>> t+(1,)
('one', 'two', 3, 1)
>>> tcopy = t+(1,)
>>> tcopy
('one', 'two', 3, 1)
>>> id(tcopy)
4604415336
>>> id(t)
4605245696
It can be seen tuple address after performing two objects is not the same operator +
0x02 array.array
If you Pythonare to use other languages like "array" data structure, we need to use arraythe module up. It is characterized by a variable, the value of the same type storage, can not store objects.
Because arraywhen the element used to specify the data type, so it is more than listand tuplehas a more space-efficient performance.
# 使用时指定元素数据类型为`float`
>>> arr = array.array('f', (1.0, 1.5, 2.0, 2.5))
>>> arr
array('f', [1.0, 1.5, 2.0, 2.5])
# 修改一个元素
>>> arr[1]=12.45
>>> arr
array('f', [1.0, 12.449999809265137, 2.0, 2.5])
# 删除一个元素
>>> del arr[2]
>>> arr
array('f', [1.0, 12.449999809265137, 2.5])
# 增加一个元素
>>> arr.append(4.89)
>>> arr
array('f', [1.0, 12.449999809265137, 2.5, 4.889999866485596])
# 如果将一个字符串类型数据存储到一个浮点数的数组将会报错
>>> arr[0]='hello'
TypeError: must be real number, not str
Data type array elements can refer to the table
| Type code | C Type | Python Type |
|---|---|---|
| ‘b’ | signed char | int |
| ‘B’ | unsigned char | int |
| 'In' | Py_UNICODE | Unicode character |
| ‘h’ | signed short | int |
| ‘H’ | unsigned short | int |
| ‘i’ | signed int | int |
| ‘I’ | unsigned int | int |
| ‘l’ | signed long | int |
| ‘L’ | unsigned long | int |
| ‘q’ | signed long long | int |
| ‘Q’ | unsigned long long | int |
| ‘f’ | float | float |
| ‘d’ | double | float |
0x03 sequence string str
Python3Use strobjects to represent a text character sequence (see this with Javastrings Stringhow similar is it). It features immutable Unicodesequence of characters.
In stra String object that is each element.
>>> s ='123abc'
>>> s
'123abc'
>>> s[0]
'1'
>>> s[2]
'3'
# 字符串是不可变的序列，不能删除其中的元素
>>> del s[1]
TypeError: 'str' object doesn't support item deletion
# 要对字符串进行操作，可以转化成list
>>> sn = list(s)
>>> sn
['1', '2', '3', 'a', 'b', 'c']
>>> sn.append(9)
>>> sn
['1', '2', '3', 'a', 'b', 'c', 9]
# 字符串中的元素也是字符串对象
>>> type(s[2])
<class 'str'>
>>> type(s)
<class 'str'>
+ str object can also perform operation, it also generates a new object for storage.
>>> s2 = s+'33'
>>> s2
'123abc33'
>>> id(s2)
4605193648
>>> id(s)
4552640416
0x04 bytes
bytes object for storing a sequence of bytes, which is characterized by non-change memory can store values of 0-256.
>>> b = bytes([0,2,4,8])
>>> b[2]
4
>>> b
b'\x00\x02\x04\x08'
>>> b[0]=33
TypeError: 'bytes' object does not support item assignment
>>> del b[0]
TypeError: 'bytes' object doesn't support item deletion
0x05 bytearray
bytearrayObjects with bytessimilar, for storing a sequence of bytes. It is characterized by variable, dynamically expansion byte array.
>>> ba = bytearray((1,3,5,7,9))
>>> ba
bytearray(b'\x01\x03\x05\x07\t')
>>> ba[1]
3
# 删除一个元素
>>> del ba[1]
>>> ba
bytearray(b'\x01\x05\x07\t')
>>> ba[0]=2
>>> ba[0]
2
# 添加一个元素
>>> ba.append(6)
# 只能添加字节
>>> ba.append(s)
TypeError: 'str' object cannot be interpreted as an integer
>>> ba
bytearray(b'\x02\x05\x07\t\x06')
# 字节的范围是0-256
>>> ba[2]=288
ValueError: byte must be in range(0, 256)
bytearrayIt can be converted into bytesan object, but not very efficient.
# bytearray转成bytes将生成一个新对象
>>> bn = bytes(ba)
>>> id(bn)
4604114344
>>> id(ba)
4552473544
0x06 each type interconversion
tuple->list
>>> tuple(l)
('a', 'b', 'c')
list->tuple
>>> t
('a', 'b', 'c')
>>> list(t)
['a', 'b', 'c']
str->list
>>> l = list('abc')
>>> l
['a', 'b', 'c']
list->str
>>> l
['a', 'b', 'c']
>>> ''.join(l)
'abc'
str->bytes
>>> s = '123'
>>> bytes(s)
TypeError: string argument without an encoding
>>> bytes(s,encoding='utf-8')
b'123'
# 或者使用str的encode()方法
>>> s.encode()
b'123'
bytes->str
>>> b = b'124'
>>> b
b'124'
>>> type(b)
<class 'bytes'>
>>> str(b,encoding='utf-8')
'124'
# 或使用bytes的decode()
>>> b.decode()
'124'
0x07 summary
These data types are Pythonbuilt-in, should select the appropriate data type in accordance with the specific needs of the actual development. For example, when the element type to be stored is diverse, then it should be used listor tuple. And array.arrayrelatively speaking, have better performance space, but it can only store a single type.
I believe in many business scenarios listor tuplewhen is to meet the needs, but also to understand other data structures, when we do some basic components, consider the performance data structures, or read other people's code can do hearts There are several.