Decypher complex (to me) statement

[PreservedKillich]

I am a C/C++ programmer (I have an inkling of classes and OOD) who has just been given his first Python task. My former co-worker who enjoyed code obfuscation wrote the following line of code:

event_arr = [x for x in _485_trace.split(" ") if x]

This is applied to a string with the format:

UC_COMMAND,bOptionalArg1,bOptionalArgN\n

where UC_COMMAND is an all uppercase string.
It has 0 or more positive int arguments, separated by a comma and exactly one blank (b) and terminated with a newline.

It looks to me like an array is being created and I infer from the brackets a list is being created on the fly. I think I understand the for clause but not the preceding 'x' nor the trailing 'if x'/

Your assistance would be much appreciated.

[wavic]

It is called list comprehension.
And it is equivalent to:

event_arr = []
for x in _485_trace.split(" "):
    if x:
        event_arr.append(x) # the first x in the expression

[x for x in _485_trace.split(" ") if x] appends x to event_arr if there is non-empty x.
str.split method splits the strin by a blank characters so the argument " " is not necessary.

[ichabod801]

Are you sure it isn't event_arr = [x for x in _485_trace.split(",") if x]? As wavic says, split with a space will split where there is a space. However, there are no spaces in the sample input you gave. It seems like comma separated values, so I'd think you would pass a comma to split to get ["UC_COMMAND", "bOptionalArg1", "bOptionalArgN\n"].

[buran]

Are you sure it isn't event_arr = [x for x in _485_trace.split(",") if x]? As wavic says, split with a space will split where there is a space. However, there are no spaces in the sample input you gave. It seems like comma separated values, so I'd think you would pass a comma to split to get ["UC_COMMAND", "bOptionalArg1", "bOptionalArgN\n"].

I started to write more or less same question then I saw he uses b as a placeholder for blank:

0 or more positive int arguments, separated by a comma and exactly one blank (b)

UC_COMMAND, OptionalArg1, OptionalArgN\n

So I guess they want to keep comma after the integer

[wavic]

Btw, welcome to the forum!

[PreservedKillich]

Thanks everyone.