Python Learning notes (i)

1) Read the book saying that at runtime, the Python interpreter compiles the code file into a temporary file. And with. PYc as the extension. Before 3.2, on the west side of the same directory, after 3.2, it will be under the _pycache_ directory. But I didn't find it. The idea of doing so increases the speed of the runtime and does not know how to force it to execute. 2) PVM: Running the. PYc. Actually this needless to say, I also do not have the ability to know this concrete is what. 3) several different implementations.          1.cppython. Standard implementation          2.pypy, it is said that the operating efficiency will be a bit higher.          3.jpython and Ironptython, respectively, capable of running in both Java and. NET environments.          4.stackless. Python is in concurrency. In fact, I still don't quite understand this. Doesn't python support multithreading? 4) Module/script: Simply saying is a source file. It seems to be a running unit of Python. This is different from Java. The operation of Java is actually logical and physical. 5) Unix script: The first line needs to be special. #! Python path:   also consider permissions. There is a clever notation. #! /usr/bin/env python6) Import and from import: In Python, import feels like a Java import before executing. At the same time from just tell where to go import7) module Attribute:moudle attribute is just a variable in a module. However, it is important to note that once the import is made, the variable becomes gobal. This is dangerous. 8) Dir/help. A good tool. All attribute inside the module can be obtained. Dir (modulename) or Help (modulename) 9) Exec. Example:exec (Open (' script1.py '). Read ()). Look at this code, you should know what to do with it. Release object.  for exmple. Object = 0. Memory will be ASARelease of P. In fact, this is very different from Java. Java is the ghost knows when it will be released. List comprehention operation will be more efficient. Type (object) to obtain the types information for object. variable:       variable creation: When the first assignment is made, it is created.        variable type: A variable does not have any type of galaxy or type restriction.        variable use: When a variable appears in an expression, it is immediately replaced by the object it directs. Refer to a variable is actually just refer to the object that this variable refers to.     If you know Java. It feels really good to understand. Java is also a variable point to an object. Unlike Java, however, Python's variable does not actually have type detection. This is a big difference. A = 3 of what is done.       1. Create an object that represents 3.      2. Variable A is created, if it does not already exist.       3. Create a connection to variable a and object 3.    15) Garbage-collection: The book says, this is instantaneous, that is, immediately. At the same time, it is based on reference count. Finally, it checks the circle reference. and then delete. 16) An explanation of a noun, share reference: Multiple vairable point to the same object17) caches: To put it simply, Python caches some interge and string for performance. You can then use the following methods, or how many of them are in the cache.          import sys         sys.getrefcount ()) Objec equal  &nbsp ;   = =. Value equal      is. Oject equal. Can actually be understood to be equal to the address. ) string type:       1) str, is Unicode text.        2) bytes:binary data        3) ByteArray, a mutable variables.  &n Bsp   Both single and double quotes can be used in two ways, String format.         ".....%s ..."% (values)         "... {} ... ". Format (values) 21) Let's talk about my first image of Python, which is that Python gives more overloads of operators than Java. This makes the specific statement look more concise. For example, in Java, there are only a few types that can be used. But in Python it's a lot more.

Python Learning Note (i)