[learning progress on June 3]

1.Git command 

2. Python- Refactoring functions 
# 10.4.3 restructure   Divide the code into a series of functions that do specific work , This process is called refactoring .
#  Refactoring makes the code clearer 、 Easier to understand 、 It's easier to expand .
#  Most of the logic can be put into one or more functions .
def greet_user():
    """ Greeting users , And point out the name """
    filename2 = 'username.json'
    try:
        with open(filename2) as file_obj:
            username = json.load(file_obj)
    except FileNotFoundError:
        username = input(' What is your name? ？')
        with open(filename2, 'w') as file_obj:
            json.dump(username, file_obj)
            print(' We will remember you when you come back ,' + username + '.')
    else:
        print(' welcome back ,' + username + '.')


greet_user()


#  Let's reconstruct the function greet_user(）
def get_stored_username():  #  New function 
    """ If the user name is stored , Just get it """
    filename2 = 'username.json'
    try:
        with open(filename2) as file_obj:
            username = json.load(file_obj)
    except FileNotFoundError:
        return None
    else:
        return username


def get_new_username():
    """ Prompt the user to enter a user name """
    username = input(' What is your name? ？')
    filename2 = 'username.json'
    with open(filename2, 'w') as file_obj:
        json.dump(username, file_obj)
    return username


def greet_user():
    """ Greeting users , And point out the name """
    username = get_stored_username()
    if username:
        print(' welcome back ,' + username + '.')
    else:
        username = get_new_username()
        print(' We will remember you when you come back ,' + username + '.')


greet_user()

#  notes ：  Each function performs a single and clear task , We call greet_user(), Print a message , Or welcome old users back , Or greet new users .
#  First call get_stored_username(), Calling get_new_username()

3. mysql 

such as ：“ . ”, '[ ]', ' | ', ' - ', Wait, there are other characters , How can I match these characters ？

Example ：select vend_name from django_apps_vendor where vend_name regexp "." order by 
| vend_name      |
+----------------+
| ACME           |
| Anvils R Us    |
| Furball Inc.   |
| Jet Set        |
| Jouets Et Ours |
| LT Supplies    |
+----------------+

Such output is not the output we want , So we also need to use before matching special characters \\.

\\-： On behalf of the match -, \\.： On behalf of the match .

select vend_name from django_apps_vendor where vend_name regexp "\\." order by vend_name;
+--------------+
| vend_name    |
+--------------+
| Furball Inc. |
+--------------+

This is the output we want . This processing is called escape . All characters with special meanings in regular expressions must be escaped in this way . Include ：. | [ ] And other special characters used so far .

\\t \\r \\n \\f \\v ： It means something different .

Mysql Two backslashes are required ：\\ Mysql Explain one for yourself ,regexp Explain another by yourself .

Match character class ：

Numbers , Letter , And numbers and letters .

[:alnum:]： Represents any letter or number （a-z A-Z 0-9).

[:alpha:] ： Any letter

[:digit:] ： Numbers

[:xdigit:]： Hexadecimal number (a-f A-F 0-9)

[:lower:]

[:upper:]

[:space:] ： Any white space character (\\t \\r \\n \\f \\v)

[:cntrl:] ASCII Control characters （0-31 and 127）

[:blank:] ： Spaces and tabs

Match multiple instances ：

* ,+, ？,{n},{n,},{n,m}

0 One or more matches ,*

1 One or more matches +

0 Or 1 A match ？

A specified number of matches {n}

No less than the specified number of matches {n,}

The range of the number of matches {n,m ,m No more than 255}

select prod_name from django_apps_product where prod_name regexp "\\([0-9] sticks?\\)" order by prod_name;
+---------------+
| prod_name     |
+---------------+
| TNT(1 stick)  |
| TNT(5 sticks) |
+---------------+
\\([0-9] sticks?\\) ：\\( matching ),[0-9],sticks? matching stick and sticks,? matching 0 A or a , send s Become optional ,

\\) matching )

my_firstDB> select prod_name from django_apps_product where prod_name regexp "[[:digit:]]{4}" order by prod_name;
+--------------+
| prod_name    |
+--------------+
| JetPack 1000 |
| JetPack 2000 |
+--------------+
"[[:digit:]]{4}" ： Match any number as 4 position

select prod_name from django_apps_product where prod_name regexp "[0-9][0-9][0-9][0-9]" order by prod_name;
+--------------+
| prod_name    |
+--------------+
| JetPack 1000 |
| JetPack 2000 |
+--------------+
Locator ：

^ $ [[:>:]] [[:<:]]

The text begins The end of the text , The beginning of words , Ending of words

select prod_name from django_apps_product where prod_name regexp "^[0-9\\.]" order by prod_name;
+--------------+
| prod_name    |
+--------------+
| .5 ton anvil |
| 1 ton anvil  |
| 2 ton anvil  |
+--------------+

^ ： Two meanings of ：[^123] Denying

^[0-9\\.]： Indicates the beginning of the text .

like and regexp： Use locators (^ and $)like Can reach and regexp The same thing .

ordinary regexp test

select "hello" regexp "[0-9]";
+------------------------+
| "hello" regexp "[0-9]" |
+------------------------+
| 0                      |
+------------------------+

0 Represents a mismatch ,1 On behalf of the match . Obviously hello There are no numbers in .

Chapter ten - Create fields