How to use the command "with" conditionally without duplication of code
Question:
I am trying to use with before executing a block of code, but only if a condition is met, but (at least the common) usage of with doesn’t appear to support that unless I duplicate the block of code.
More concretely, I know I can do the following:
if condition:
with blah_blah():
my_code_block
else:
my_code_block
But that’s unsatisfying during development since any change I make to my_code_block must be made twice. What I want to do (conceptually) is:
if condition:
with blah_blah():
else:
my_code_block
That doesn’t work, though. Is there a way to accomplish what I’m trying to do?
For anyone that’s interested in my particular use, I’m trying to write code that runs a batch of examples in pytorch, with torch.no_grad() if I’m in evaluation mode and without it if I’m in train mode. So what I want to do becomes
if mode == 'eval':
with torch.no_grad():
else:
run_batch(features, labels)
Answers:
Use the with statement, but with a nullcontext context manager if necessary.
from contextlib import nullcontext
with blah_blah() if condition else nullcontext():
my_code_block
nullcontext takes an optional argument that it will return if your with statement expects something to be bound with as. For example,
with nullcontext("hello") as f:
print(f) # outputs "hello"
I was wondering if it could be accomplished with:
def myrunner(myfunc,usecontext=True):
if usecontext:
with blahblah():
myfunc()
else:
myfunc()
def myfunc()...
myrunner(myfunc,usecontext=false)
But looking at it, I don’t see how the context can effect myfunc.
I am trying to use with before executing a block of code, but only if a condition is met, but (at least the common) usage of with doesn’t appear to support that unless I duplicate the block of code.
More concretely, I know I can do the following:
if condition:
with blah_blah():
my_code_block
else:
my_code_block
But that’s unsatisfying during development since any change I make to my_code_block must be made twice. What I want to do (conceptually) is:
if condition:
with blah_blah():
else:
my_code_block
That doesn’t work, though. Is there a way to accomplish what I’m trying to do?
For anyone that’s interested in my particular use, I’m trying to write code that runs a batch of examples in pytorch, with torch.no_grad() if I’m in evaluation mode and without it if I’m in train mode. So what I want to do becomes
if mode == 'eval':
with torch.no_grad():
else:
run_batch(features, labels)
Use the with statement, but with a nullcontext context manager if necessary.
from contextlib import nullcontext
with blah_blah() if condition else nullcontext():
my_code_block
nullcontext takes an optional argument that it will return if your with statement expects something to be bound with as. For example,
with nullcontext("hello") as f:
print(f) # outputs "hello"
I was wondering if it could be accomplished with:
def myrunner(myfunc,usecontext=True):
if usecontext:
with blahblah():
myfunc()
else:
myfunc()
def myfunc()...
myrunner(myfunc,usecontext=false)
But looking at it, I don’t see how the context can effect myfunc.