To write onto multiple files on the same time (a number of files are variable),
I'd like to code as follows, for example, IF I can do,
LIST_LEN = 4
with [ open('list_%d.txt' % i, 'w') for i in range(LIST_LEN) ] as fobjlist:
for i in range(1000):
fobjlist[random.randrange(LIST_LEN)].write(str(i)+"\n")
or using a dict object,
DICT_KEYS = ('foo', 'bar', 'baz')
with { k: open('dict_%s.txt' % k, 'w') for k in DICT_KEYS } as fobjdict:
for i in range(1000):
fobjdict[random.choice(DICT_KEYS)].write(str(i)+"\n")
However, list and dict don't has __exit__ method and so they cannot run.
One idea is using contextlib.nested(),
from contextlib import nested
with nested(*[open('list_%d.txt' % i, 'w') for i in range(LIST_LEN)]) as
fobjlist:
for i in range(1000):
fobjlist[random.randrange(LIST_LEN)].write(str(i)+"\n")
with nested(*[open('dict_%s.txt' % k, 'w') for k in DICT_KEYS]) as fobjlist:
fobjdict = dict(zip(DICT_KEYS, fobjlist)) #convert list to dict
for i in range(1000):
fobjdict[random.choice(DICT_KEYS)].write(str(i)+"\n")
On Python2.x, this is OK. but 3.x warns that nested() is deprecated.
Moreover, on using dict, it is required to convert list to dict.
Another idea is to make container classes having __exit__() myself.
class MyList(list):
def __enter__(self):
return [ v.__enter__() for v in self ]
def __exit__(self, exc_type, exc_value, traceback):
ret = False
for v in self:
if v.__exit__(exc_type, exc_value, traceback):
ret = True
exc_type = exc_value = traceback = None
return ret
class MyDict(dict):
def __enter__(self):
return { k: v.__enter__() for k, v in self.items() }
def __exit__(self, exc_type, exc_value, traceback):
ret = False
for v in self.values():
if v.__exit__(exc_type, exc_value, traceback):
ret = True
exc_type = exc_value = traceback = None
return ret
with MyList( open('list_%d.txt' % i, 'w') for i in range(LIST_LEN) ) as
fobjlist:
for i in range(1000):
fobjlist[random.randrange(LIST_LEN)].write(str(i)+"\n")
with MyDict( (k, open('dict_%s.txt' % k, 'w')) for k in DICT_KEYS ) as fobjdict:
for i in range(1000):
fobjdict[random.choice(DICT_KEYS)].write(str(i)+"\n")
I think this is smarter a little than others,
but it cannot guaranteed to call __exit__() of members in containers
if members are changed during with-context.
So, do you have another, more smart and pythonic way?
Thanks
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