One hour Python per day (10.11)

3.1 The assignment of a Python variable

The equal sign (=) is the primary assignment symbol: Anint = astring = ' Hanxingzhi '

However, it is important to note that the assignment is not assigning a value to a variable.

3.1.1 Chain assignment and value-added assignment

x = y = 1 (multiple Assignment)

y = x = x + 1 (chained Assignment)

x = x + 1 ======> x + = 1 This is the same as the value-added assignment effect used by C #, but it is not possible to use the + + and--pre-and post-increment self-decrement operations in Python.

multivariate assignment : I have to say that Python has multiple assignments that I don't know about.

' Hanxingzhi '>>> x1>>> y3>>> z'Hanxingzhi '

We'd better use tuples in real programming to use multivariate assignments

>>> (x, y, Z) = (hanxingzhi')>>> 1>>>  y2>>> z'hanxingzhi'

Application of Multivariate assignment:

In Python we can use multivariate assignments to exchange values of two variables without using intermediate variables.

>>> (x, y) = 1,2>>> x, y = y,x>>> (x, y) (2, 1)

Those identifiers for 3.2 python

The most I feel about Python identifiers is the use of underscores:

1. _xxx do not import ' from mdule import * '

2. _xxx_ system-defined name

3. Private variables in the _xxx class

Note: Because underscores have special meanings for compilers and are symbols used by built-in identifiers, it is possible to use fewer underscores as identifiers when programming. Generally speaking, _xxx is defined as private.

3.2.1python BASIC Programming Style

Note: Use # to Annotate

Documentation: Python provides a mechanism for dynamically retrieving document strings by _DOC_ special variables. In a module, a class declaration, or a function declaration, the first string that is not assigned can be accessed using OBJ._DOC_, where obj is the name of a module, class function.

Indent: 4 spaces should be indented.

3.2.2 Module structure and layout

# (1) Start line (Unix) = = Only the starting line is used in a UNIX environment, and the starting line can only enter the script name to execute the script. Do not invoke the interpreter directly.

# (2) Module document = = A simple introduction to the function of the module, and the meaning of the important local variables, outside the module can be accessed through MODULE._DOC_ access to the content.

# (3) Module import = = Imports All modules required for the current code, each module is imported only once, and the module import code inside the function will not execute unless the function is running.

# (4) Variable definition = = defines a global variable, all functions of this module can be used. But from a good programming style, unless you try to use local variables instead of global variables.

# (5) class definition statement = = All classes are defined here, and the class statement is executed when the module is imported. The document variable for the class is CLASS._DOC_

# (6) function definition statement = = function defined here grams can be accessed externally through module.function (). The document variable for the function is FUNCTION._DOC_

# (7) Main function = = Of course the main function can write the test code.

One hour Python per day (10.11)