1. The OS module
Files and directories are processed
Directory: This is a folder
Properties:
Os.name: View the current system type;
If it’s Windows –> NT
If it is MAX –> POSIX
Os. environ: Returns the environment variables of the current system (all)
Function:
Os.environ. get() : Gets one of the specified environment variables
Path classification:
Absolute path: The path with the disk runroot directory is the absolute path
pyhton
Relative path: A path value relative to a file (reference); Features: writing without disk characters
Os.getcwd () : Returns the full path (absolute path) of the currently executing.py file
Os. listdir(PATH) : Displays all files and directories in the PATH path
Os.mkdir (path) : Create a single-level folder. This method can only create directories. If the directory already exists, the creation fails
Os. makedirs(path) : Create a multi-level folder (cascading new). This method can only create directories. If the directory already exists, the creation fails, and an error is sent
Os.rmdir (path) : Deletes a single-level folder. This method can only delete the page game directory. If the directory does not exist, the deletion fails
Os. removedirs(path) : Removes multiple layers of folders (cascading). This method can only remove directories. If the directory does not exist, the creation fails
Os.remove (path) : Delete the file, if the file does not exist, report an error! [Note] This method can only delete files, not directories
Os. rename(old, new) : You can rename a file or directory
Os.system () : Execute system instructions: CLS, ipconfig, www.sangpi.comdir…
Os.path. join(PATH, fileName) : The concatenation of data in PATH and fileName is called a new path and is returned as a string
Os.path. isdir(path) : determines whether the contents of the path corresponding to a directory, and if so, returns True; Otherwise, it returns False
Os.path. isfile(path) : determines whether the contents of the path corresponding to the file are a file, and if so, returns True; Otherwise, it returns False
Os.path.exists (path) : Determine whether the content of the path corresponding to exists, if so, return True; Otherwise, it returns False
Os.path.getSize (PATH) : The capacity of the corresponding path content is checked, and the number of bytes is returned
Os.path.basename (path) : Passing in a path value returns the last/last part of the path
Os.path.dirname (path): Passing in a path value returns the last/previous portion of the path
Os.path. split(path) : Passing in a path value puts the last/preceding part of the path into the first element of the primitive,
/ The next part goes into the second element of the primitive
Os.path.splitext (path) : Passing in a path value will take the last one of this path. In the first element of the primitive ancestor,
And the following into the second element of the primitive
1. Character Set (character encoding) :
ASCII:
US standard size, range: find it yourself
Unicode code:
Universal code, it can contain Chinese, but unfortunately, it is not universal.
Utf-8 code:
Most popular on computers, it contains content from previous Unicode and extends it,
It can also save Chinese
UTF-8 holds Chinese characters. Each Chinese character takes up to three bytes.
GBK code:
Our Chinese code watch, it also inherited the GB2312, mainly used in some Chinese systems
GBK saves Chinese characters, and 1 Chinese character takes up 2 bytes of memory.
2. Bytes and characters
Remember: Everything in a computer is in bytes (storage)
Characters: we use a text editor to open, can read (not garbled), is the character file
Byte: we use the text editor to open, can not read, is the byte file
Consider: Is the file at the end of.doc a character file?
Not;
3. File reading
There are prescribed steps:
1). Open the file
2). Operate data (read and write)
3). Close file **
Open the file:
Fp = open(path, encoding=,errors=’Ignore’)
Operation data:
Open mode:
‘r’ : denotes readonly character (readonly)
#’r+’ : Added a write function to the read-only function
‘W’ : means to write only characters (readWrite), the first write, if you do not close the file, continue to write, then the original content will be overwritten
#’w+’ : Appends a read function to the write-only function
‘A’ : Indicates additional content
#’a+’ : Added a read function while keeping appended content
‘rb’ : denotes read-only bytes (binary data)
‘wb’ : means write section only (binary data)
Encoding:
If the code set does not show the definition, the corresponding is: GBK
We can also define UTF-8 according to our own needs
Errors:
If you do not write, the default is an error (encoding/decoding is inconsistent).
We can also say ignore, so we won’t get any errors, but we’ll get some garbled code
Encoding & Decoding:
Encoding: program –> file
Decode: file –> program
Remember: if the encoding and decoding do not match, it will be garbled (in Chinese).
Read the data from the file:
Fp = open (path, ‘r’)
Content = fp.read() # Read all content
Content = fp.read(num) # Read the number of bytes in num
Content = fp.readline() # Read a line
Content = fp.readlines() # Reads all lines and returns them as a list
Print (content) # Print the content read
[Note] Read the file, if the file does not exist, simply say: FileNotFounderError
Write data to a file:
fw= open(path, ‘w’)
Fw. Write (str1) # Writes the contents of str1 variable to the file corresponding to path (overwrite)
[Note] Write the file, if the file does not exist, create the file first, then write the content; If it exists, overwrite the previous content
fw = open(path, ‘a’)
Fw. Write (str1) # Writes the contents of str1 variable to the file corresponding to path (append)
Close the file:
Fp.close () # Close file (release resource)