Rect (, screen. width (), screen. height () pixbufGdk. pixbuf_get_from_window (rootwin, * rect) # Where * rect is?
Rect = (0, 0, screen. width (), screen. height () pixbuf = Gdk. pixbuf_get_from_window (rootwin, * rect) # What is * rect?
Reply: I will not use PyGObject for pure discussion.
Asterisk ParameterThis syntax.
Similar Problem (may be helpful to you ):
Define function def func (** kwargs): Do print kwargs need func (a = 1, B = 2, c = 3) when calling a function? Dict_t = {'A': 1, 'B': 2, 'C': 3} Can't the dictionary be directly transmitted? For example, func (dict_t ). Is there any good way?
Python parameter knowledge (meaning of adding a star before a variable)
Let's get the meaning of the asterisk parameter and two examples:
Use an asterisk before the parameter name to make the function accept any number of positional parameters.
The two asterisks accept any number of keyword parameters.
Example of location parameters:
Assume that you have the following requirements:
Output all parameters received by a function except the first parameter.
Keyword parameter example:
No matter how many keyword parameters you pass in, I can find them in kw.
Next, let's take a look at the example in the supplementary information you provided in the question:
The following example accepts any number of location parameters and only outputs the first parameter.
(Here the type of s is tuples)
Let's define a new metagroup, which will be thrown to the mean function later.
Differences between the two usage methods:
As you can see, after an asterisk is used, a is unpacked. Split them into parameters and threw them in.
The above example is equivalent:
======================== 2013-2-26 update ==============================
S is a tuple, so the value cannot be modified.
Here I am trying to change the 1st values in the location parameter to 5 and then output them.
Use the tuples to see:
Let's switch to the list to see:
Use a string to see:
Here we split the list, the tuples, and the string is converted into a location parameter and then passed in.
You can see that. S is a tuples.
Type of the s variable that stores the Location Parameter
It does not depend on the type of the input parameter.
======================== Write more examples =========================:
Common functions:
Literary functions:
The mean traverses all output location parameters. S is a tuples. Don't forget.
Let's split the list and strings.
Split tuples:
Dictionary Splitting:
If you split the dictionary, it only transmits the [Key]. You cannot obtain the value.
====== The value of the dictionary to be split. You can use two asterisks for function parameters. ========
This means that all keyword parameters are thrown to s (excluding location parameters)
When using functions, When using functions,
The two asterisks in front of c only represent the form of splitting c into a keyword parameter.
When used, we split the dictionary into keyword parameters.
Function receiving is also a keyword parameter. Therefore, no error is reported.
It is equivalent to the following: (No error reported, haha .) (No error reported, haha .)
If you use a function with only one asterisk:
Or do not give an asterisk:
Errors are reported. Errors are reported.
Why ??
Put one asterisk:
Put an asterisk in front of the dictionary.
If you split the dictionary with One asterisk, only the [Key] is passed in. The previous example proves that.
The problem is that our function mean only accepts the keyword parameter (Let's review the definition of mean before ): There is nothing in s. Output? Error! There is nothing in s. Output? Error!
Without an asterisk:
Without an asterisk, you can directly throw the dictionary.
The problem is that function parameters ** s only accept keyword parameters.
S. There is nothing in it. An error is returned!
(
Function NameAnd
Parameter NameThey are all random and have no special significance .)
I feel that my example is not very good. If you get confused.
Welcome to discussion in the comment area .:)
Extended reading:
StackOverflow explains the asterisk Syntax:
Syntax-Python: Once and for all. What does the Star operator mean in Python?
Reference Value passing:
Python: How do I pass a variable by reference?
This parameter is expanded and passed in. It is equivalent:
pixbuf = Gdk.pixbuf_get_from_window(rootwin, 0, 0, screen.width(), screen.height())
Call (caller)
Func (* sequence) Pass all objects in sequence as inpidual positional arguments
Seq = [1, 2, 3]
Func (* seq)-> func (1, 2, 3)
Func (** dict) Pass all key/value pairs in dict as inpidual keyword arguments
Dict = {'A' = 1, 'B' = 2}
Func (* dict)-> func (a = 1, B = 2)
Function-defined
Def func (* name) Matches and collects remaining positional arguments in a tuple
Func (1, 2, 3)-> name = [1, 2, 3]
Def func (** name) Matches and collects remaining keyword arguments in a dictionary
Func (a = 1, B = 2)-> dict = {'A' = 1, 'B' = 2}
See The asterisks in Chapter 18. Argumentspython have two meanings:
1. When defining a function
Generally, function parameters take a specified number of parameters, such
def func(a, b, c): print a, b, c
We recommend a post: Understanding '*', '* args', '**' and '** kwargs'
>>> Def test (* args, ** kwargs ):
... Print args, kwargs
>>> A = {"a": 1, "B": 2}
>>> Test ()
({'A': 1, 'B': 2 },){}
>>> Test (* a) # It is equivalent to test ('A', 'B ')
('A', 'B '){}
>>> Test (** a) # It is equivalent to test (a = 1, B = 2)
() {'A': 1, 'B': 2}
An asterisk is used to disassemble a sequence. If the variable itself is a dictionary, it degrades to a sequence of keys.
The two asterisks are used to disassemble and pass in the key-value pair.
Let's just consider it a syntactic sugar. PORTER: 1.2 decompress the files that can be iterated and assign values to multiple variables
This decompress is very dedicate and has a lot of elegant skills.
Summary:
(1)
No exchange of tem intermediate variables is required at all:
A, B = B,
(2)
Sometimes, you may only want to extract a part of it and discard other values. In this case, Python does not provide special syntax. However, you can use any variable name to place a placeholder, and then you can discard these variables.
>>> data = [ 'ACME', 50, 91.1, (2012, 12, 21) ]>>> _, shares, price, _ = data
