About design mode (II)
(it also includes the knowledge content of modules and packages)
Read the picture file and copy the file
with open('Picture name','rb') as f: #b is binary
with open('New file name','wb') as w:
for line in f.readlines():
w.write(line)
print('Picture copy complete')pickle serialization and deserialization
pickle.dump(obj,file) obj is the object to be serialized, and file refers to the stored file
pickle.load(file) reads data from file} and reversely serializes it into an object
import pickle with open(r"d:\data.dat","wb") as f: a1="jiaqi" a2=234 a3=[20,30,40] #Serialize objects into files pickle.dump(a1,f) pickle.dump(a2,f) pickle.dump(a3,f) #Deserialize the obtained data into objects import pickle with open(r"d:\data.dat","rb") as f: a1=pickle.load(f) a2=pickle.load(f) a3=pickle.load(f) print(a1) print(a2) print(a3)
Operation of CSV file
In CSV file:
Values have no type and all values are strings
You cannot specify the width or height of a cell. You cannot merge cells
Styles such as font color cannot be specified
No more sheets
Cannot embed image chart
#Reading and writing CSV files
import csv
with open("dd.csv","r") as f: #dd is the file name
a_csv = csv.reader(f)
for row in a_csv: #Traverse the contents of the file
print(row) #read
with open("ee.csv","r") as f: #ee is the file name
b_csv = csv.writer(f)
b_csv.writerow(["ID","full name","Age"])
b_csv.writerow(["1001","jiajia","18"])
c = [["1002","dfg","19"],["1003","fhj","20"]]
b_csv.writerows(c) #write inos and os Path module
The os module can help us directly operate the operating system. We can directly call the executable files and commands of the operating system,
Direct operation of files, directories, etc
os.system can help us call system commands directly
os.system calls the Notepad program of windows system
import os
os.system("notepad.exe")
os.system call windows In the system ping command
import os
os.system("ping www.baidu.com")
#GBK
Is Ping www.a.shifen.com [36.152.44.95] Data with 32 bytes:
From 36.152.44.95 Reply from: byte=32 time=35ms TTL=54
From 36.152.44.95 Reply from: byte=32 time=24ms TTL=54
From 36.152.44.95 Reply from: byte=32 time=26ms TTL=54
From 36.152.44.95 Reply from: byte=32 time=21ms TTL=54
36.152.44.95 of Ping statistical information :
data packet: has been sent = 4，Received = 4，lose = 0 (0% lose)，
Estimated round trip time(In Milliseconds ):
minimum = 21ms，Longest = 35ms，average = 26msMethods of common operation files under OS module
| remove(path) | Delete the specified file |
| rename(str.dest) | Rename a file or directory |
| stat(path) | Returns all properties of the file |
| listdir(path) | Returns the list of files and directories in the path directory |
| mkdir(path) | Create directory |
| makedirs(path1/path2/path3/...) | Create multi-level directory |
| madir(path) | Delete directory |
| removedirs(path1/path2/path3/...) | Delete multilevel directory |
| getcwd() | Return current working directory: current work dir |
| chdir(path) | Set path to the current working directory |
| walk() | Traverse the directory tree |
| sep | The path separator used by the current operating system |
os.path module
| isabs(path) | Determine whether the path is an absolute path |
| isdir(path) | Determine whether the path is a directory |
| isfile(path) | Determine whether the path is a file |
| exists(path) | Judge whether the file in the specified path exists |
| getsize(filename) | Returns the size of the file |
| abspath(path) | Return absolute path |
| dirname(p) | Returns the path of the directory |
| getatime(filename) | Returns the last access time of the file |
| getmtime(filename) | Returns the last modification time of the file |
| walk(top,func,arg) | Traversing directories recursively |
| join(path,*paths) | Connect multiple path s |
| split(path) | Split the path |
| splitext(path) | Splits the extension of the file from the path |
import os
import os.path #from os import path
print(os.path.isabs("file name"))
path = os.path.abspath("")
print(os.path.split(path))walk() recursively traverses all files and directories
os.walk() method:
Returns a tuple of three elements, (dirpath,dirnames,filenames)
dirpath: the path to list the specified directory
dirnames: all folders in the directory
filenames: all files in the directory
import os
path = os.getcwd()
list_ifles = os.walk(path)
for dirpath,dirnames,filenames in list_files:
for dir in dirnames:
print(dir)
for file in filenames:
print(file)
import os
all_files = []
path = os.getcwd()
list_ifles = os.walk(path)
for dirpath,dirnames,filenames in list_files:
for dir in dirnames:
all_files.append(os.path.join(dirpath,dir))
for file in filenames:
all_files.append(os.path.join(dirpath,file))
#Print files for all subdirectories
for file in all_files:
print(files)shutil module (copy and compression)
import shutil
shutil.copytree("Copied file","New file")(New file (need not exist)
shutil.copytree("","",ignaore=shutil.ignore_patterns("*.txt","*.html")) At this time, the new file can be the original one
#Compression and decompression
shuttil.make_archive("","","") The second is a compressed format, such as zip
The third is the compressed file
The first is the compressed address
#Compression method when shutil is not used
z1=zipfile.ZipFile("Compressed address","w")
z1.write("Compressed file")
z1.close()
z2=zipfile.ZipFile("Files to be unzipped","r")
z2.extractall("Unzip to directory")
z2.close()
Module import
import module name
There are four general categories of modules:
1. Code written in Python (. py file)
2. c or c + + extensions that have been compiled as shared libraries or DLL s
3. Package a set of modules
4. A built-in module written in c and connected to the Python interpreter
from...import imports the members (functions or classes) in the module
Import of packages
1,import a.aa.module_AA
When using, you must add a full name to reference, such as a.aa module_ AA. fun_ AA()
2,from a.aa import module_AA
When using, you can directly use the module name. For example: module_AA.fun_AA()
3,from a.aa.module_AA import fun_AA # direct import function
When using, you can directly use the function name, such as fun_AA()
Note:
1. In the syntax from package import item, item can be package, module, function, class and variable
2,import item1. Item 2 or other modules in this package must not have item 2 syntax
__ init__. Three core functions of Py:
1. As the identification of the package, it cannot be deleted
2. Used to implement fuzzy import
3. The essence of importing a package is execution__ init__.py file, which can be found in__ init__.py file to initialize this package.
And the need for uniform code execution