Python basic data type details (GO)

1, Empty (None)
Indicates that the value is an empty object, and the null value is a special value in Python, denoted by none. None cannot be understood as 0, because 0 is meaningful, and none is a special null value.
2. Boolean Type (Boolean)
In Python, none, 0 in any numeric type, empty string "", Empty tuple (), empty list [], empty dictionary {} are treated as false, and custom types, if the __nonzero__ () or __len__ () method is implemented and the method returns 0 or FALSE, The instance is also treated as false, and the other objects are true
The Boolean value is exactly the same as the Boolean algebra, with a Boolean value of only true, false two, or true, or false, in Python, which can be used to indicate a Boolean value directly with True, false (note case), or by Boolean operations:

1 The code is as follows: 2 >>> true3true4 >>> False5  False6 >>> 3 > 27True8 >>> 3 > 59 False

Boolean values can also be operated with and, or, and not.

1). And operations are associated with operations, and only the result of all True,and operations is true:

 and truetrue  and Falsefalse  and Falsefalse

2). The or operation is or operation, as long as one of the true,or operation results is true:

or truetrue or falsetrue or Falsefalse

3). The not operation is a non-operation, it is a single-mesh operator that turns true into False,false true:

 not TrueFalse  not falsetrue

4). Boolean values are often used in conditional judgments, such as:

if age >=:    print'adult'else:     Print ' teenager '

3, Integral type (INT)
In Python, the processing of integers is divided into ordinary integers and long integers, the ordinary integer length is the machine bit long, usually 32 bits, the integer over this range automatically when the long integer processing, and the range of long integers is almost completely unlimited
Python can handle integers of any size, including, of course, negative integers, which are represented in the program in the same way as mathematically, for example: 1,100,-8080,0, etc.
4. Float type (float)
Python's floating-point number is a decimal number in mathematics, similar to a double in the C language.
In operations, the result of an integer and floating-point operation is a floating-point number
Floating-point numbers, which are decimals, are called floating-point numbers because, when represented by scientific notation, the decimal position of a floating-point number is variable, for example, 1.23x109 and 12.3x108 are equal. Floating-point numbers can be written in mathematical notation, such as 1.23,3.14,-9.01, and so on. But for very large or very small floating-point numbers, it must be expressed in scientific notation, the 10 is replaced with E, 1.23x109 is 1.23e9, or 12.3e8,0.000012 can be written 1.2e-5, and so on.
Integers and floating-point numbers are stored inside the computer in different ways, and integer operations are always accurate (is division accurate?). Yes! ), and the floating-point operation may have rounding errors.
5. Strings (String)
Python strings can be enclosed in single quotes or double quotes, or even enclosed in three quotation marks.
strings are arbitrary text enclosed in ' or ', such as ' abc ', ' XYZ ', and so on. Note that the ' or ' itself is only a representation, not a part of the string, so the string ' abc ' only a,b,c these 3 characters. If ' itself is also a character, then you can use "", such as "I m OK" contains the characters are I, ', M, space, o,k these 6 characters.

What if the inside of a string contains both ' and contains '? You can use the escape character \ To identify, for example:

' i\ ' m \ "Ok\"! '

The string content represented is:

I'm "OK"!

Escape character \ Can escape many characters, such as \ n for newline, \ t for tab, character \ itself to escape, so \ \ means the character is \, you can print a string in Python's interactive command line to see:

Print ' i\ ' m OK. ' I ' m OK. Print ' i\ ' m learning\npython. ' I ' M Learning Python. Print ' \\\n\\ ' \

If there are many characters in the string that need to be escaped, you need to add a lot of \, in order to simplify, Python also allows to use R ' ' to indicate that the inside of the string is not escaped by default, you can try it yourself:

Print ' \\\t\\ ' \        print r'\\\t\\'\\\t\\

If there is a lot of line wrapping inside the string, writing in a row is not good to read, in order to simplify, Python allows the "..." format to represent multiple lines of content, you can try it yourself:

Print " " line1 line2 ... line3 " " Line1line2line3

The above is entered in the interactive command line, if written as a program, that is:

Print " " Line1line2line3 " "

Multi-line string ' ... ' can also be used in front with R, please test yourself.
6. Lists (list)
The list is represented by the symbol [], and the middle element can be any type, separated by commas. List similar to array in C, for sequential storage structure
Built-in functions:

Append (x) append to the end of the chain extend (L) append a list, equivalent to + =Insert (i,x) in position i insert X, the remaining elements are pushed backwards, if I is greater than the list length, at the end of the add, if I is less than 0, Just at the beginning add remove (x) to delete the first value of the element x, if not present will throw an exception reverse () inversion sequence pops ([i]) return and delete the element where I is, I default to the last element index (x) returns the position of x in the first occurrence of the list, Does not exist then throws an exception count (x) returns x number of occurrences of sort () Len (list) returns the length of list del list[i] Delete list specified in i+  1 variable slice slices refer to part of the extraction sequence in the form of: List[start:end:step]. The rule is that the default step size is 1, but it can also be customized. 

7, tuple (tuple)
A tuple is a data structure similar to a list, but it cannot be changed once it is initialized, faster than a list, and the tuple does not provide dynamic memory management capabilities, so you need to understand the rules:
A tuple can use the subscript to return an element or a sub-tuple
The method that represents a tuple that contains only one element is: (d,) followed by a comma, which is used to distinguish it from a separate variable
8. Set (SET)
Collections are unordered, non-repeating sets of elements, like collections in mathematics, that can be performed in logical and arithmetic operations
9. Dictionary (Dict)
A dictionary is an unordered storage structure that includes a keyword (key) and a value that corresponds to a keyword (value). The format of the dictionary is: dictionary = {Key:value}. A keyword is an immutable type, such as a string, an integer, a tuple that contains only immutable objects, and a list that cannot be used as a keyword. If there is a keyword pair in the list, you can construct the dictionary directly with Dict ()

Python basic data type details (GO)