Python's first week of study notes _ to be added (3)

Python built-in data structures First, the numerical type 1. Data type classification: int: integer

Python3 int is a long integer with no size limit and is limited by the size of the memory area
int (x) returns an integer

float: floating point

There are integers and fractional parts. Supports decimal and scientific notation notation. Only double-precision.
Float (x) returns a floating-point number

Complex: plural

There are real and imaginary parts, the real and imaginary part are floating-point numbers, 3+4.2j
Complex (x), complex (Y) returns a complex number

BOOL: Boolean

Subclass of int, only 2 instances True, false corresponds to 1 and 0, can be directly calculated with integers
BOOL (x) returns a Boolean value, and the bool value judgment logic is as described earlier, such as:
BOOL (")---False
BOOL (0)---False

2. Numeric processing functions: (1) int (), floor (), ceil (), round (),///difference: Int ():

Builtin built-in functions
Official Document Description:
class int (x=0)
class int (x, base=10)
Return an integer object constructed from a number or string x, or return 0 if no arguments is given. If x is a number, return x.int(). For floating point numbers, this truncates towards zero.

If x is not a number or if base is given, then x must are a string, bytes, or ByteArray instance representing an integer li Teral in Radix base. Optionally, the literal can be preceded by + or – (with no space in between) and surrounded by whitespace. A base-n literal consists of the digits 0 to n-1 and with A to Z (or A to Z) has the values of 35. The default base is 10. The allowed values are 0 and 2–36. Base-2,-8, and-16 literals can be optionally prefixed with 0b/0b, 0o/0o, or 0x/0x, as with the integer literals in code. Base 0 means to interpret exactly as a code literal, so then the actual base is 2, 8, ten, or, and so that int (' 010 ', 0) Is isn't legal, while INT (' 010 ') are, as well as int (' 010 ', 8).

For floating-point numbers, truncate decimals to 0
That is, take the whole number of parts

Floor ():

Math Template
Rounding down

Ceil ():

Math Template
Rounding up

Round ():

Four homes six into five to take even

//:

Divide and Floor ()
Floored quotient of X and Y

(2) Digital processing function _2min ()

Min (iterable, [, Key, default])
Min (arg1, arg2, args[, key])

Max ()

Max (iterable, [, Key, default])
Max (Arg1, arg2, args[, key])

Pow (x, y)

Same function as X**y

MATH.SQRT ()

Prescribing

Bin ()

The return value is a string

Oct ()

The return value is a string

Hex ()

The return value is a string

MATH.PIMATH.E (3) Type-judging types (obj)

return type rather than string

Isinstance (obj, class_or_tuple)

Returns a Boolean value

Second, Sequence object Data type classification: 1.STR: string 2.list: List

The elements in the list are in order and can use the index
A linear data structure
The list is mutable

Initialization
Cases:

lst=list()lst=[]lst=[1,2,‘a‘,[‘i‘,‘j‘]]lst=[range(5)]

Size can not be defined at the beginning, compared to Java

List, linked lists, queue, stack differences

List linear storage, high query efficiency O (n), insert, delete inefficient O (n)
Linked list scattered in memory, query efficiency low O (n), insert, delete high efficiency O (1)
Queue FIFO First
Stack LIFO LIFO

List Index Access

Positive index: From left to right, starting with 0, numbering each element in a list
Negative index: From right to left, starting from-1

List Query

Index (Value,[start,[stop]])
Returns the index of the first occurrence
Can only traverse from left to right
No match to return ValueError exception
Time complexity O (n), because of the need to traverse the list

Count (value)

Returns the number of occurrences of the value in the list
Time complexity O (n), because of the need to traverse the list

Len ()

Time complexity O (1)
Counter performs a count on each insertion and deletion to the list
Therefore, when you call Len (), only the counter value is typed and no traversal is performed

List increment, insert element append (object), None

Append at tail, return none
Modify an existing object without generating a new object
Time complexity O (1)

Insert (Index, object), None

Inserts an element at the specified index, returning none
Modify an existing object without generating a new object
Time complexity O (n), because subsequent elements may occur after insertion in memory to move back in and out of action

If the index is not error-bound:
Beyond the upper bound, trailing append
Beyond the Nether, head append

Extend (iteratable), None

Appends elements of an object that can be iterated back, returning none
Modify an existing object without generating a new object

+ List

Connection operation, connecting two lists
Create a new object, the original list does not change
The add() method is essentially called

* List

Repeat, repeat the list element n times to return the new list

Attention:

x=[[1,2,3]]y=x*3y[0][1]=200y

The result is:
[[1, 200, 3], [1, 200, 3], [1, 200, 3]]

y = [1]*5y[0] = 6y[1] = 7print(y)

The result is:
[6, 7, 1, 1, 1]

Can be temporarily understood as:
* Copy, for complex objects, copy the reference, not the data, the copied three elements actually point to the same memory address
Simple objects do not affect

List Delete element Remove (value), None

Finds the first value that matches value from left to right, removes the element, and returns none
Modify an existing object without generating a new object
Time complexity O (n), because subsequent elements may occur in memory after insertion (the list is stored sequentially in memory)

Pop ([index]), item

An element is popped from the tail of the list without specifying index
Specifies index, which pops an element from the index, and the index bounds throws a indexerror error
Complexity of Time:
Do not specify an index of O (1)
Specifies that the index is O (n) because subsequent elements may occur in memory after the insertion (the list is stored sequentially in memory)

Clear (), None

Clears all elements of the list, leaving an empty list

List other operations reverse ()-None

Reverses the list element, returning none
Modify an existing object without generating a new object

Sort (Key=none, reverse=false), None

Sort list elements by default ascending
Modify an existing object without generating a new object
Reverse is true, reversed, descending
Key A function that specifies how key is sorted

In3.tuple: meta-Group Three, key-value pairs Data type classification: set: Set Dict: Dictionary

Python's first week of study notes _ to be added (3)