python To efficiently use the result of function in if statement

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Is there any other code form, that one can both use a function in if statement and get the value of function without executing the function twice?

For example,

There exists a function, fun1(arg), which takes an hour to return its result (The result value can be either None or some int)

and I want to do some further calculation(for example get its squared value) only if the result from fun1 is not None.

This will be done by:

result = fun1(arg) 
if result: 
    result = result * result

Is there any shorter form such as

if (result = fun1(arg)):
    result = result * result

in python?


It may be more "clean" in a code manner, it is possible in C/C++ to do the 2nd one. Not in Python to the best of my knowledge. Moreover, the two examples you gave have the exact same needs in term of memory and computation. So it would be totally equivalent to use any of these two.

The two are absolutely identical. So my answer would be, go with your first method that you already know how to code đź‘Ť.

Do not over complicate when it is not necessary, it is a good piece of advice in general.

3.1. If Statements, It is the type of the results of true-false conditions or tests. In the jump function definition use an if - else statement (hint [3]). Most statements fit neatly on one line, and the creator of Python decided it was best to make the syntax simple in  Since the return statement terminates the execution of the current function, the two forms are equivalent (although the second one is arguably more readable than the first). The efficiency of both forms is comparable, the underlying machine code has to perform a jump if the if condition is false anyway. Note that Python supports a syntax that


This is coming in a future version of python. See the following PEP

https://www.python.org/dev/peps/pep-0572/

It'll be known as an assignment expression. The proposed syntax is like;

# Handle a matched regex
if (match := pattern.search(data)) is not None:
    # Do something with match

4. More Control Flow Tools, Perhaps the most well-known statement type is the if statement. Another place pass can be used is as a place-holder for a function or conditional In this example it is equivalent to result = result + [a], but more efficient. An else statement can be combined with an if statement. An else statement contains the block of code that executes if the conditional expression in the if statement resolves to 0 or a FALSE value. The else statement is an optional statement and there could be at most only one else statement following if.


No you can't do this. Statements in Python not work as expressions in C with ;.

4. More Control Flow Tools, The keyword ' elif ' is short for 'else if', and is useful to avoid excessive indentation​. In most such cases, however, it is convenient to use the enumerate() function, see In this example it is equivalent to result = result + [a] , but more efficient. Save the example program jumpFuncStub.py as jumpFunc.py , and complete the definitions of functions jump and main as described in the function documentation strings in the program. In the jump function definition use an if - else statement (hint [3] ). In the main function definition use a for -each loop, the range function, and the jump function.


Well the second possible solution you wrote is incorrect since the 'result' variable in the if statement has no preassigned value. I would simply go with the first one...

Python IF, ELSE, ELIF, Nested IF & Switch Case Statement, In this tutorial, learn Conditional Statements in Python. Learn how to use If, Else, Elif, Nested IF and Switch Case Statements with examples. Code Line 9: The line print st will output the value of variable st which is "x is less than y", function​(argument){ switch(argument) { case 0: return "This is Case  Python also accepts function recursion, which means a defined function can call itself. Recursion is a common mathematical and programming concept. It means that a function calls itself. This has the benefit of meaning that you can loop through data to reach a result.


What you are trying to do in your 2nd code is assignment inside expressions, which can't be done in Python.

From the official docs

Note that in Python, unlike C, assignment cannot occur inside expressions. C programmers may grumble about this, but it avoids a common class of problems encountered in C programs: typing = in an expression when == was intended.

also, see:

http://effbot.org/pyfaq/why-can-t-i-use-an-assignment-in-an-expression.htm

Time Efficiency of IF statements vs. Python Dictionaries – Scott Lobdell, If we define a static dictionary outside of the function, we now have a time by using dictionaries was actually less efficient in general because of the time it Then I just created my own function decorator to time the results:. Python | Output using print() function The simplest way to produce output is using the print() function where you can pass zero or more expressions separated by commas. This function converts the expressions you pass into a string before writing to the screen.


If the function intention is better expressed by a signature with an extensible number of positional arguments, it can be defined with the *args constructs. In the function body, args will be a tuple of all the remaining positional arguments.


Another benefit of print () being a function is composability. Functions are so-called first-class objects or first-class citizens in Python, which is a fancy way of saying they’re values just like strings or numbers. This way, you can assign a function to a variable, pass it to another function,


The python return statement is used to return values from the function. We can use the return statement in a function only. It can’t be used outside of a Python function.