Example of _ call _ usage in Python and python _ call _

Example of _ call _ usage in Python and python _ call _

This article describes the usage of _ call _ in Python and shares it with you for your reference. The specific method is as follows:

Let's take a look at the following sample code:

# Call. py when a class is loaded. Class Next: List = [] def _ init _ (self, low, high): for Num in range (low, high): self. list. append (Num ** 2) def _ call _ (self, Nu): return self. list [Nu]

If you use this method:

b = Next(1,7)print b.Listprint b(2)

The feedback is normal:

[1, 4, 9, 16, 25, 36]9

However, if you use:

b = Nextb(1,7)print b.Listprint b(2)$python ./call.py[1, 4, 9, 16, 25, 36]Traceback (most recent call last): File "cal.py", line 17, in <module>  print b(2) TypeError: __init__() takes exactly 3 arguments (2 given)

_ Init _ is an initialization function that is executed when the class instance is generated.

While _ call _ is a simulated () call and needs to be applied on the instance. Therefore, the instance has already executed _ init.

The following example:

b = Next

This is not to create an instance, but to assign the class to a variable. Therefore, the subsequent operations using B are for the Next class, which is actually:

Next(1,7)print Next.Listprint Next(2)

I hope this article will help you with Python programming.

** Prefix usage in python. Here is an example (with points)

Def fun (p, ** args ):
Print args

Fun (1, a = 2, B = 3, c = 4, d = 5)

Call usage in batch processing is described in detail with examples,

Call another batch processing program from the batch processing program.

CALL [drive:] [path] filename [batch-parameters]

Batch-parameters specifies the command line information required by the batch processing program.

If the command extension is enabled, the CALL will change as follows:

The CALL command now accepts the volume label as the CALL target. Syntax:

CALL: label arguments

A new batch file context is created by a specified parameter and controlled by the volume label
And then passed to the statement. You must "exit" twice by reaching the last two times of the batch script file.
When a file is read for the first time, the control will return to the end of the CALL statement. Second
Will exit the batch script. Type GOTO /?, See GOTO: Description of the EOF extension,
This description allows you to return from a batch of scripts.

In addition, the batch script text parameter reference (% 0, % 1, etc.) has changed as follows:

% * In the batch script indicates all parameters (for example, % 1% 2% 3% 4% 5 ...)

The substitution of the batch parameter (% n) has been enhanced. You can use the following syntax:

% ~ 1-delete quotation marks (") and expand % 1
% ~ F1-extended % 1 to a fully qualified path name
% ~ D1-only expand % 1 to one drive letter
% ~ P1-only expand % 1 to one path
% ~ N1-only expand % 1 to one file name
% ~ X1-only expand % 1 to one file extension
% ~ S1-expanded path refers to short name
% ~ A1-extended % 1 to file attributes
% ~ T1-extend % 1 to the date/time of the file
% ~ Z1-expand % 1 to the file size
% ~ $ PATH: 1-find the directory of the PATH environment variable and set % 1
Extended to the first fully qualified name found. If the environment
The variable name is not defined, or the file is not found.
Extended to a null string

You can combine the modifier to obtain multiple results:

% ~ Dp1-extend % 1 to drive letter and path only
% ~ Nx1-only extend % 1 to the file name and extension
% ~ Dp $ PATH: 1-find % 1 in the directory column in the PATH environment variable,
And extend to the drive letter and path of the first file.
% ~ Ftza1-extend % 1 to output rows similar to DIR.

In the preceding example, % 1 and PATH can be replaced by other valid values.
% ~ The syntax is terminated by a valid parameter number. % ~ The modifier cannot match % *
Use

From: cmd --> call /? > Xxx.txt

Respondent: bmgeng-Level 3

Report the Call statement to Call another program and wait until it is executed to return correct or wrong results.
The returned position is C... the remaining full text>