A few things to remember while coding in Python
satyajit.ranjeev.in
A few things to remember while coding in Python
1–10 of 146 posts
Re: A few things to remember while coding in Python
#2Another handy one I saw recently:
varname, = [x for x in l if predicate_with_single_truth_value(x)]
Re: A few things to remember while coding in Python
#3My only complaint with this list is conditional assignments. They make it harder for me to understand the code. I am used to the if being at the start and when it isn't it takes more time for me to parse what the real meaning of the line is.
Re: A few things to remember while coding in Python
#4Another handy one I saw recently: varname, = [x for x in l if predicate_with_single_truth_value(x)] The comma after varname is an implicit assert that the list comprehension only contains one element.
Trailing commas are really easy to miss. When reading this line of code, I did not notice it immediately; I originally assumed that varname was being assigned a list.
This sort of code would be very confusing when I'm just quickly reading through a procedure trying to find the potential bug.
Re: A few things to remember while coding in Python
#5It's worth explaining why mutable defaults are bad.
The problem with mutable defaults is that they are evaluated once only when the function is defined. Each time the function is called you'll be using the same mutable variable that was created during function definition.
Re: A few things to remember while coding in Python
#6Another handy one I saw recently: varname, = [x for x in l if predicate_with_single_truth_value(x)] The comma after varname is an implicit assert that the list comprehension only contains one element.
Trailing commas are really easy to miss. When reading this line of code, I did not notice it immediately; I originally assumed that varname was being assigned a list. This sort of code would be very confusing when I'm just quickly reading through a procedure trying to find the potential bug.
Indeed. I prefer the following variant which is more explicit and thus (IMHO) more in the spirit of Python:
(varname,) = [x for x in l if predicate_with_single_truth_value(x)]Re: A few things to remember while coding in Python
#7Another handy one I saw recently: varname, = [x for x in l if predicate_with_single_truth_value(x)] The comma after varname is an implicit assert that the list comprehension only contains one element.
Trailing commas are really easy to miss. When reading this line of code, I did not notice it immediately; I originally assumed that varname was being assigned a list. This sort of code would be very confusing when I'm just quickly reading through a procedure trying to find the potential bug.
Agreed. It could be written much more clearly in my opinion like this:
[varname] = [x for x in l if predicate_with_single_truth_value(x)]Re: A few things to remember while coding in Python
#8Another handy one I saw recently: varname, = [x for x in l if predicate_with_single_truth_value(x)] The comma after varname is an implicit assert that the list comprehension only contains one element.
Trailing commas are really easy to miss. When reading this line of code, I did not notice it immediately; I originally assumed that varname was being assigned a list. This sort of code would be very confusing when I'm just quickly reading through a procedure trying to find the potential bug.
You could also use the ,= operator, of course:
varname ,= [...]
Re: A few things to remember while coding in Python
#9Till now I had never seen Ellipsis. It seems very similar to slice notation [:]. Found an StackOverflow comment [1] that has more details about usage of Ellipsis in slicing higher dimensional array numpy.
[1] http://stackoverflow.com/questions/118370/how-do-you-use-the...
Re: A few things to remember while coding in Python
#10[deleted]