Common system modules and file operations

One 、time modular

1. Time stamp
   Use the specified time to 1970 year 1 month 1 Japan 0 when 0 second （ Greenwich mean time ） The time difference （ The unit is seconds ） The way to express time is timestamp

Be careful ： Greenwich mean time and Beijing time are 8 Hour time difference

4 Bytes （ Timestamp storage time ）
16 Bytes （ Use string to store time ）

import time

1. time.time()    --   Get the current time 
print(time.time())      # 1627612143.562589


2.
time.localtime()  --   Get the local time of the current time , Returns the structure time 
time.localtime( Time stamp )   --   Convert the time corresponding to the timestamp into local time 
t1 = time.localtime()
print(time.localtime(1627612143.562589))
print(time.localtime(0))


3. time.sleep( Time )     --   Program hibernate for a specified time , Unit second 
time.sleep(2)
print('==========')

time.strftime( Time format , Structure time ) Structure time to string time
xxx year xx month xx Japan xx when ：xx branch ：xx second

‘’’
%Y - year
%m - month
%d - Japan
%H - when （24 Hours ）
%I - when （12 Hours ）
%M - branch
%S - second
%p - AM、PM( In the morning 、 Afternoon )
%a - Abbreviations of English words of week
%A - Spelling English words on Sunday
%b - English abbreviation of month
%B - Month English spelling
‘’’

result = time.strftime('%Y year %m month %d Japan  %H:%M:%S', t1)
print(result)

# xxxx-xx-xx xx:xx:xx
result = time.strftime('%Y-%m-%d %H:%M:%S', t1)
print(result)

result = time.strftime('%m month %d Japan  %p%I:%M %B', t1)
print(result)

5. Convert string time to structure time

time.strptime( String time , Time format )
t2 = '2010-10-2'

t3 = time.strptime('2010-10-2', '%Y-%m-%d')
print(f' Zhou {
      t3.tm_wday+1}')
print(t3)

6. Convert string time to timestamp （ First convert the string time into the structure time ）

time.mktime( Structure time )  --   Convert structure time to timestamp 
result = time.mktime(t3)
print(result)

Two 、datetime modular

import datetime
from datetime import datetime

1. datetime type – Processing time including year, month, day, hour, minute and second
   1） establish datetime Time object

datetime(year,moth,day, hour=0, minute=0, second=0)
t1 = datetime(2010, 10, 2)
print(t1)           # 2010-10-02 00:00:00


t2 = datetime(2011, 9, 30, 11, 15, 30)
print(t2)           # 2011-09-30 11:15:30

2） Get time attribute
Time object .year、 Time object .month、…

print(t2.month)
print(t2.hour)

3. Get the current time

t3 = datetime.now()
print(t3)

4. take datetime Convert to structure time

t4 = t3.timetuple()
print(t4)

5. take datetime Convert to string time

st5 = t3.strftime('%Y year %m month %d Japan  %a')
print(st5)

6. Convert string time to datetime

st6 = '2003-7-1'
t5 = datetime.strptime(st6, '%Y-%m-%d')
print(t5)

2.timedelta - It is mainly used for time addition and subtraction

from datetime import timedelta
t6 = t5 + timedelta(days=45)
print(t6)

t7 = t5 - timedelta(hours=8)
print(t7)

t8 = t5 + timedelta(days=1, hours=5, minutes=15)
print(t8)

3、 ... and 、hashlib modular

import hashlib

# hashlib modular  -  For generating data hash Abstract 

‘’’
hash Encryption algorithms mainly include ：md5 and shaxxx

1. hash Features of encryption ：
   a. Irreversible （ After encrypting the original data （ Generated summary ） Unable to restore ）
   b. The same data is generated by the same algorithm （ Ciphertext ） It's the same
   c. Data of different sizes have the same length of summaries generated by the same algorithm

2. Use hashlib Generate a summary of the data
   ‘’’

   1. Create according to the algorithm hash object

hashlib. Algorithm name ()
hash = hashlib.md5()

2.  Add data 

hash object .update( binary data )
pw = '123456'
hash.update(pw.encode())

f = open('files/text.py', 'rb')
hash.update(f.read())

3.  Get a summary 

result = hash.hexdigest()
print(result)

‘’’
python Binary data type – bytes
String and bytes Mutual conversion of

1. str --> bytes
   Method 1 ：bytes( character string , ‘utf-8’)
   Method 2 ：b’ character string ’
   Method 3 ： character string .encode()

2. bytes --> str
   Method 1 ：str( binary data , ‘utf-8’)
   Method 2 ： Binary system .decode()
   ‘’’

#  String to binary 
print(bytes('abc', 'utf-8'))        # b'abc'

b1 = b'abc'
print(type(b1))         # <class 'bytes'>

str1 = 'abc'
print(str1.encode())

#  Binary to string 
print(str(b1, 'utf-8'))
print(b1.decode())

Four 、 File operations

1. Data storage
   ‘’’
   The data saved in the program is stored in the running memory by default , The data in the running memory will be released at the end of the program .
   If you want the data generated during the operation of the program not to be destroyed after the end of the program , You need to store data on disk .

The process of storing data to disk is called data persistence 、 Data localization .
The basic principle of data persistence - Store data on disk through files .
‘’’

2. File operations （ Operation file content ）
   ‘’’
   File operation mainly solves two problems ：a. How to store the data in the program to disk through files
   b. How to use the data saved in the file in the program
   ‘’’

3. Basic steps of file operation
   ‘’’
   First step ： Open file
   open( File path , Read write mode ,encoding= File encoding ) – Open the specified file in the specified way , Return file object
   1） File path – Location information of the file in the computer , Provide values as strings .
   a. Absolute path ： The full path of the file in the computer
   b. Relative paths ：. – Represents the current directory （ The directory where the current code file is located ）,./ It can be omitted
   … – Represents the upper directory of the current directory

2. Read write mode – Set whether the read operation or write operation is supported after opening the file ; Set whether the type of operation data is string or binary
   The first set of values ：
   r – read-only
   w – Just write ; Clear the original file first
   a – Just write ; Keep the contents of the original file , Add data to the back
   Second set of values ：
   t – The data type is string （t You can ignore ）
   b – The data type is bytes

            'r' == 'rt' == 'tr'
   

   Be careful ： If it is a text file, you can use t perhaps b The way to open , If it is a binary file, you can only b The way to open

3. encoding – File encoding ( The encoding method of the open file must be consistent with that of the file )
   With b When opening a file in the way encoding Can't assign a value

The second step ： Reading documents 、 Writing documents
File object .read()
File object .write( data )

The third step ： Close file
File object .close()
‘’’

 Parameters 1： route 
open('files/text.py')
open('../day-14 Common system modules and file operations /01-review.py')

 Parameters 2： Read write mode 
1) r  --   read-only 
f = open('test.py', 'r')
f.read()

2) w  --   Just write ;  Will empty the original file 
f = open('test.py', 'w')
f.write('abc')
f.read()

3) t  --   The type of read / write data is string 
f = open('test.py', 'rt')
result = f.read()
print(type(result))     # <class 'str'>

f = open('test.py', 'at')
f.write('abc')

4) b  --   The type of read-write data is binary 
f = open('text.py', 'rb')
result = f.read()
print(type(result))         # <class 'bytes'>

f = open('test.py', 'ab')
f.write('abc'.encode())

f = open('02-time modular .py', mode='r', encoding='utf-8')
f.read()

f = open('files/text.py', 'r', encoding='utf-8')
f.read()
f = open(r'E:\ wallpaper \2.jpg', 'rb')
f.read()
f.close()

5、 ... and 、 Read and write operations

1. Read operations
‘’’
1)
File object .read() – Read from the read-write position to the end of the file （ The read / write location is at the beginning of the file by default ）
File object .readline() – Read from the reading and writing position to the end of a line （ Only valid when reading text files ）
Text object .readlines() – Line by line reading , After reading
‘’’

f = open('files/text.py', encoding='utf-8')
result = f.read()
print(result)

print('------------------- Gorgeous split line --------------------')
f.seek(0)       #  Set the read / write position to the beginning of the file 
print(f.read())

print('------------------- Gorgeous split line --------------------')
f.seek(0)
print(f.readline())
print(f.readline())
print(f.readline())
print(f.readline())
print('===:', f.readline(), '====', sep='')

print('------------------- Gorgeous split line --------------------')
f.seek(0)
print(f.readlines())
f.close()

print('------------------- Gorgeous split line --------------------')
f = open('test.py', 'a', encoding='utf-8')
f.write('\nabc\n123\n456')
# f.writelines(['abc', '123', '456'])
f.close()

6、 ... and 、 Data memory operation

The basic steps of data persistence ：
‘’’
First step ： Identify the data that needs to be persisted （ Determine which data to use the next time you run the program ）
The second step ： Create a file to save the initial value of data
The third step ： When this data is needed in the program, read the data from the file
Step four ： If the data changes , Write the latest data back to the file
‘’’

 practice 1： Write a program and print the number of times the program runs 
'''  Run the program for the first time to print ： 1  Run the program for the first time to print ： 2  Run the program for the first time to print ： 3 '''
f = open('count.txt', 'rt', encoding='utf-8')
count = int(f.read())
count += 1
print(count)

f = open('count.txt', 'w', encoding='utf-8')
f.write(str(count))

 practice 2： Add student , And display all student information after adding （ Just need the student's name ）
'''  Please enter the student's name ： Xiao Ming   Xiao Ming  [' Xiao Ming ']  Please enter the student's name ： floret   Xiao Ming   floret  [' Xiao Ming ', ' floret ']  Please enter the student's name ：q （ Program end ）  Please enter the student's name ： Zhang San   Xiao Ming   floret   Zhang San  [' Xiao Ming ', ' floret ', ' Zhang San ']  Please enter the student's name :  Li Si   Xiao Ming   floret   Zhang San   Li Si  [' Xiao Ming ', ' floret ', ' Zhang San ', ' Li Si ']  Please enter the student's name :q （ Program end ） '''


 demand 1：
while True:
    name = input(' Please enter the student's name ：')
    if name == 'q':
        break

    f = open('count.txt', 'a', encoding='utf-8')
    f.write(f'{
      name} ')

    f = open('count.txt', encoding='utf-8')
    print(f.read())


 demand 2：
while True:
    name = input(' Please enter the student's name :')
    if name == 'q':
        break

    f = open('coun1.txt', encoding='utf-8')
    all_count = eval(f.read())    # '[]', "['name']"
    all_count.append(name)
    print(all_count)

    f = open('coun1.txt', 'w', encoding='utf-8')
    f.write(str(all_count))