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This article is to share with you about how to understand the basic data types of python. The editor thinks it is very practical, so I share it with you. I hope you can get something after reading this article.

I. basic usage

1. Annotation

In Python, the # + statement is either a comment or a comment block

# Life is too short, I use Python2. Output

In Python, print () is the output function

Print ("Hello World!") 3. Variable

What is a variable?

Memory space and stored values:

Understanding of num = 10

Assign 10 to the memory space of a variable called num

4. Naming convention

Variable names can use letters, numbers, and underscores "_"

Cannot start with a number

Strictly case-sensitive

Do not use Chinese

Do not use keywords

In addition, the naming conventions of variables are applicable to script names and later function names and other command specifications.

5. The way variables are defined

In Python, you do not need to specify the data type to define variables

# the first variable definition method a = 10b = 2 "the second definition method a _ r _ b = 30 ~ 40

Thinking: how to exchange data between the following two variables

# define two variables a = 10b = 20 variables' normal way, complete the exchange of variable data c = aa = bb = centering variables # use the syntax of python definition of comparison variables to realize the data exchange of variables a _ (B) = b, a _ (II), python

The type () function, which returns the current data type

Data type classification

String string

Numeric type Number

Integer int

Floating point float

Complex number

Boolean bool

List list

Tuple tuple

Dictionary dict

Set set

Variable data types: list, dictionary, collection

Immutable data types: strings, numbers, tuples

Container type data: strings, lists, tuples, collections, dictionaries

Non-container type data: numeric, Boolean type

1. String type

Both single and double quotation marks can define a string, which needs to be wrapped manually

Three quotation marks can define a string that wraps lines automatically

Quotation marks can be nested within each other, but not within themselves

Escape characters can be used in strings, such as\ r\ n\ t

If you do not want to implement escaped characters in a string, you can add love = r'\ nihao\ shijie' to the character definition.

# the definition method is to use single quotation marks or double quotation marks love = 'iloveyou'hello = "Hello World" # you can also use three quotation marks to define a large string, which is generally used to define a large text string, and a large string can be wrapped with s =' 'for example, the content of this very, very long article.'' two。 Numeric type

# numeric type Number'''int integer float floating point type complex plural bool Boolean type can be automatically converted to numeric type (True 1meme false 0)''varn = 521varn =-1111varn = 3.1415926varn = 0x10 # hexadecimal varn = bread001100111' # bytes# plural varn = 5' 6j # complex# numeric type can participate in the operation a = 10b = 20print (aplural) 3.List list type

A list is used to represent a series of data

The data stored in the list can be of any type

Define using square brackets []

Each data is separated by a comma

Each set of data stored in the list is called an element

Get the element by subscript

There are lists in the list called secondary lists or multi-level lists.

About the subscript 0 1 2 3 4 in the list [definition of the 1'''4.tuple tuple type in 5-4-3-2-tuple type

Tuples are defined using parentheses ()

The only difference between tuples and lists is that the value cannot be changed.

Vart = (1, 2, 2, 3) other definitions of # tuples, vart = 1, 2, and 3

Note: when defining a tuple, if there is only one element in the tuple, you need to add "," otherwise it is not a tuple type.

Vart = (1,) 5.Dict dictionary type

Define using * * curly braces {} * *

Dictionary is the way to store key-value pairs name: admin

The key must be a string or numeric type, and the value can be any type

The key name cannot be repeated, and the value can be repeated.

# for example, you need to record the relevant data of a book, book title, author, price,. Vard = {'title':'','author':' ghost millet', 'price':'29.99'} # print (vard,type (vard)) # {' title':'','author':' ghost millet', 'price':'29.99'} # get the value in the dictionary print (vard [' title']) # the keys in the dictionary cannot be reused Otherwise, it will overwrite the vard = {'afiughuanglu 10, paraphrase 10 print (vard) 6.set collection type

A set collection is a data type of a collection that is unordered and has no duplicate elements.

The set collection is defined using square brackets or the set () method

You can only use the set () method if you need to define an empty collection, because the empty dictionary defined in curly braces

Sets are mainly used for operations, intersections, difference sets, union sets, symmetric sets

A = {1a.add ('b') # can't get a single element in the collection, but you can add and delete # a.discard ('a') # print (a) # check whether the current element is in the collection. # print (1 in a) # collection is mainly used for operations, intersection, difference, union Symmetrical sets a = {1pr 2pr 3pr print'} b = {1pr 2pr 3pr b'} b = {1pr 2pr 3pr 33} print (a & b) # intersects {1mlmena'} print (a-b) # subtractive sets {'byes, 2pr 3} a sets have, b sets do not have print (a | b) # union sets {1pr 2cm3,33,' aquary cognac b', 22}, put them together And remove the multiple print (a ^ b) # symmetric difference {33, 2, 3, 'bounded, 22} 7. Data type conversion

What is data type conversion?

Convert one data type to another, such as a string to a number

Why do I need data type conversions?

Because you can't operate between different data types.

What is the form of data type conversion?

Automatic type conversion

Forced type conversion

8. Automatic type conversion

When two different values are calculated, the result will be calculated to a higher precision True = > integer = > floating point = > complex number

True is converted to the number 1 and false to the number 0 in the sum operation.

9. Forced type conversion

Each data type in python has a corresponding method, which can be converted.

Str ()

Int () string is pure numeric convertible container type cannot be converted to numeric int type

The float () conversion rule is the same as the int type, resulting in a floating point type

Bool () can convert other types to Boolean True or False

False:', 0jue 0.0jue false, [], {}, (), set ()

List () list / tuple () tuple / set () collection

Numeric types cannot be converted

When converting a string, treat each character as an element

The three can be converted to each other, and the result is disordered when they are transformed into sets.

The dictionary is not completely converted, only the keys in the dictionary are retained.

Dict () dictionary

Numeric type is not a container type and cannot be converted to a dictionary

Strings cannot be directly converted to dictionaries

Lists / tuples can be converted to dictionaries, requiring a secondary list / tuple, and each secondary element can only have two values

The above is how to understand the basic data types of python. The editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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