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Closed 10 years ago.
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design of python: why is assert a statement and not a function?
In Python 3, print was made into a function. What are the benefits of having assert be a statement?
For optimization. If you run your Python script with the -O option no code will be generated for assert statements. This would not be possible if assert were a function.
See the documentation on assert, which references this behavior.
Related
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Python3 exec, why returns None?
(3 answers)
Closed 2 years ago.
print(exec("5 + 5"))
its not printing 10 but prints None instead. I'm sure exec basically executes a code.
exec returns None. You should probably use the eval() in this case
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If and elif in Python for good programming practices
(2 answers)
Closed 4 years ago.
Does someone have a simple answer as to why you would use a If If rather than an If Elif?
Example:
def fun(item):
if item[0]<'M':
return 0
if item[0]<'Q':
return 1
return 2
With a setup like this, where you are returning a value inside each if block, the if statements behave exactly the same as an if elif structure since the return exits out of the function without checking the conditions below. So, when the functionality is the same, the choice should be made on readability. explicit is better than implicit.
There is no good reason to use if statements like this implying exclusively in the conditionals, when if elif statements makes the exclusivity explicit and is much more readable and easier to maintain.
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What is the use of "assert" in Python?
(23 answers)
Closed 6 years ago.
I have gone through many source code of functional test cases written in python. Many of the code uses assert for testing equality, why so?
In most test runners, a test failure is indicated by raising an exception - which is what the assert() function does if its argument evaluates to False.
Thus assert(1 == 0) will fail, and abort that specific test with an AssertionError exception. This is caught by the test framework, and the test is marked as having failed.
The framework/test-runner then moves on to the next test.
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How to use "pass" statement?
(18 answers)
Closed 6 years ago.
What does pass mean in python? I have seen it used and I do not see why you need to use it or what it does? I guess I could say it passes over whatever function it is in, but why include it?
Quoth the doc:
The pass statement does nothing. It can be used when a statement is required syntactically but the program requires no action.
References:
https://docs.python.org/2/reference/simple_stmts.html#the-pass-statement
https://docs.python.org/2/tutorial/controlflow.html#pass-statements
"It is used when a statement is required syntactically but you do not want any command or code to execute.
The pass statement is a null operation; nothing happens when it executes. The pass is also useful in places where your code will eventually go, but has not been written yet (e.g., in stubs for example):"
https://www.tutorialspoint.com/python/python_pass_statement.htm
This question already has answers here:
Using pass on a non necessary else statement
(5 answers)
Closed 8 years ago.
Is there a preferred/proper style?
This:
def fx(Boolean):
if Boolean:
# Do stuff.
else:
pass
Or this:
def fx(Boolean):
if Boolean:
# Do stuff.
Is it preferred/proper to include else: pass if you don't want anything to happen?
I've read PEP 8 - Style Guide for Python Code and did not find anything concerning my question.
You should never include else: pass. It's superfluous. Just omit the else; it's intentionally an optional keyword.
If you don't need the else if there is no reason to add it. It will just confuse other people reading your code in the future (ie yourself a few months later).