exception - Advancing Python generator function to just before the first yield -

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• how can run initialization code generator function immediately, rather @ first call? 5 answers

when instantiate generator function, won't execute code until call next on it.

it means if generator function contains kind of of initialization code, won't executed until it's iterated on.

consider example:

def generator(filename):     open(filename) f:         data = f.read()      while true:         yield data  gen = generator('/tmp/some_file') # @ point, no generator code executed  # initialization code executed @ first iteration x in gen:     pass 

if file not exist, exception raised @ loop. i'd code before first yield execute before generator iterated over, exceptions during initialization raised @ generator instantiation.

is there clean pythonic way so?

wrap regular function around generator , put initialization there:

def file_contents_repeated(filename):     open(filename) f:         data = f.read()     return _gen(data)  def _gen(data):     while true:         yield data 

(in case, replace inner generator itertools.repeat, not in general.)