Thirteen, remove specific character string
Method a: string strip (), rstrip (), lstrip () remove both ends or either end of characters
Method two: string sections plus splicing
Method three: replace string () method of a regular expression or the re.sub () delete any substring
Four: string translate () method, you can delete many different characters at the same time
Fourteen, python text file operations
Open file: File Object Name = open (name [, mode [, buffering]])
name: a string value containing the name of the file you want to access.
mode: mode determines the open file modes: read-only, write, append and so on. See a complete list of all possible values as follows. This parameter is not mandatory, the default file is read-only access mode (r).
buffering :
If the value of buffering is set to 0, there will be storage. If the value of buffering take 1, the line will register to access the file.
If the value is an integer greater than 1 of buffering, indicating that this is the buffer size of the storage area. If negative, the buffer size for the system default parking zone.
Close file: the file name of the object .close ()
The difference between flush and close
flush (): after the data in the buffer brush to the destination, the flow may be used.
close (): after the data in the buffer brush to the destination, the flow shut down, the process is mainly used for the underlying resource ending call. This action must be done.
Fifth, set the file buffer
Full Buffer: buffering function is set to open an integer greater than 1, the number of buffer size
Line buffer: buffering function is set open (text mode can) 1
Unbuffered: buffering function is set open 0
XVI map the file into memory
purpose:
1. file mapped into memory to achieve random access to binary files
Register 2. Some embedded devices is addressed to the memory address space, you can go to access these registers by mapping
3. Multiple processes are mapped to the same file in order to achieve the purpose of the communication process
solution
Use standard library mmap.mmap () function will map the file to the memory address space
m=mmap.mmap(fileno, length[, flags[, prot[, access[, offset]]]])
fileno: file encoding, may be () obtained by file object .fileno
length: file descriptor, the object may be fileno file () method, or from os.open ()
To map the size of the file parts (bytes), this value is 0, then the entire file is mapped, if the current size is larger than the file size, the file is extended.
flags：
MAP_PRIVATE: This memory-mapped only available in this process;
mmap.MAP_SHARED: the shared memory mapping and other processes, the process of mapping all the same file, which will be able to see a change made;
prot: mmap.PROT_READ, mmap.PROT_WRITE and mmap.PROT_WRITE | mmap.PROT_READ. Meaning the last one is at the same time readable and writable.
access: access has a value in the optional parameters have mmap
ACCESS_READ: read access.
ACCESS_WRITE: write access by default.
ACCESS_COPY: copy visit, will not change writes to the file, the file is written using flush the change.
XVII uses temporary files
Without naming temporary files, it will be automatically deleted after you close, less access to the file system
Solutions standard library tempfile.TemporaryFile (anonymous), NamedRemporaryFile (named) difference between the two:
The difference is that with TemporaryFile, NamedTemporaryFile will generate a genuine document
TemporaryFile not generate real files on the hard disk, but is written in the memory
Examples
from tempfile import TemporaryFile , NamedTemporaryFile
1. Read #
f = TemporaryFile(mode="w+")
# Parameters:
# 1). Mode = "w +" allow opening mode, the default mode is w + b
# W write mode
# W + write mode
# W + b mode write Bytes
# 2). Buffering = -1 buffer size is not limited -1
# 3). Encoding = character encoding of files read None
f.write("abcdefg\nhijkmlm\nopqist\nuvwxyz") # 写入
f.seek (0) # switch the cursor to the beginning
# Line = f.readlines () # read each line in accordance with
line = f.read () # Read All
print(line)
When there is a parameter # delete = True, when the variable is cleared, the resulting file will be deleted, delete = False, the file is not deleted
from tempfile import NamedTemporaryFile
1. Read #
f = NamedTemporaryFile(mode="w+", dir=r"D:\data\01_RPA_Project")
# Parameters:
# 1). Mode = "w +" allow opening mode, the default mode is w + b
# W write mode
# W + write mode
# W + b mode write Bytes
# 2). Buffering = -1 buffer size is not limited -1
# 3). Encoding = character encoding of files read None
# 4). Dir = None temporary file storage location of the file
# 5). Delete = True variable will delete files to delete, delete = False, the variables are not deleted when deleting
print (f.name) # print the file name
f.write("abcdefg\nhijkmlm\nopqist\nuvwxyz") # 写入
f.seek (0) # switch the cursor to the beginning
# Line = f.readlines () # read each line in accordance with
line = f.read () # Read All
print(line)
XVIII instance properties do type checking
Objective: To want a statically typed language like that, their instance properties do type checking
Solution: Use Descriptor
Ninth, commonly decorator
@property
The method calls the class as a reference field properties in the same class. The modified method of characteristics, internal processing logic can be achieved, but the external call to provide a unified way. Follow the principle of unified access.
In addition, @ property can be used to achieve similar to the set and get methods in Java
@staticmethod
The methods in the class decorative static method, that is, classes without the need to create an instance of the class can be directly referenced by name. The function-arrival Example unbundling effect.
@classmethod
The first parameter is a class class method, as is the method of operating the class itself. Which class class method is called, was introduced to the class which operates as the first argument.
XX, how variable the same name into a string
solution:
Dictionary of then extracted key name
This method can not be abstracted into functions
Examples
>> abc = 376
# The first step: Dictionary of
>> dict (abc = abc) # This is the best show of the step
>> { 'abc': 376} # The resulting dictionary
# Step two: key to take a dictionary
>> dict(abc = abc).keys()
>> dict_keys ([ 'abc']) # key to obtain a version of the dictionary string
# The third step: list of
>> list(dict(abc = abc).keys())
>> [ 'abc'] # obtain a list
# At last
>> list(dict(abc = abc).keys())[0]
>> 'abc' # you want something: a string of variable name
XXI ring data structures in memory management
Problems: for example, the presence of an annular circular linked list data structures, etc. FIG referenced variable or between each reference cycle will not be automatically recovered when not needed, resulting in memory-intensive
Solution: Use weak references weakref module, reference can be a weak reference object, but does not increase the reference count, if all variables are between weak reference recovery system will be automatically
XXII, by calling the method instance method name string
Option One: calling getattr (object attribute name) (parameters)
Option II: methodcaller operator module (method name, parameters) (Method Object belongs)