Tools, FAQ, Tutorials:
Function Parameter Default Expression Executed Only Once
Is it true that the function parameter default expression is only executed once in Python?
✍: FYIcenter.com
Yes, the function parameter default expression is only executed once in Python when the "def" statement is interpreted.
For example, in the following Python code, when the "def profile()" statement is interpreted, the default value for "age" parameter will be set to 18+3 once and stay with that value:
>>> legalAge = 18 >>> def profile(name,age=legalAge+3): ... print("Name: "+name) ... print("Age: "+str(age)) ... >>> profile("Joe") Name: Joe Age: 21 >>> legalAge = 20 >>> profile("Jay") Name: Jay Age: 21
In the following example, the default expression assigned a new "list" object to parameter "x" once. When the function is called multiple times, the same "list" object is referenced again and again.
>>> def growingList(x=[1]): ... x.append(x[len(x)-1]*2) ... return x ... >>> growingList() [1, 2] >>> growingList() [1, 2, 4] >>> growingList() [1, 2, 4, 8] >>> growingList() [1, 2, 4, 8, 16] >>> growingList() [1, 2, 4, 8, 16, 32] >>> growingList() [1, 2, 4, 8, 16, 32, 64]
⇒ Variable Scope in Function Definition Statements
⇐ '*...' and '**...' Wildcard Parameters in Function Definitions
2022-10-26, 1227🔥, 0💬
Popular Posts:
How to use the urllib.request.Request object to build more complex HTTP request? The urllib.request....
Where to get a JSON.stringify() Example Code in JavaScript? Here is a good JSON.stringify() example ...
How To Create an Array with a Sequence of Integers or Characters in PHP? The quickest way to create ...
How To Loop through an Array without Using "foreach" in PHP? PHP offers the following functions to a...
How To Read a File in Binary Mode in PHP? If you have a file that stores binary data, like an execut...