[Tutor] sharing a small script someone may find of use

[Nathan Smith]

Solid advice in this email! Thanks a lot!


I admit I'd not considered using sets, I so rarely do, but it makes sense!


Fair point as well on the if check on whether it is already loaded, I 
couldn't really find much research on unloading modules, and the 
resources I could find indicated deleting with del like that could be 
dangerous without actually explaining why, so for the sake of memory 
destroying crunchy gremlins, I was like: "Hmm. This should work."


Thanks again

On 13/08/2022 03:35, Cameron Simpson wrote:
> Ooooh, feedback!
>
> On 13Aug2022 01:53, nathan tech <nathan-tech at hotmail.com> wrote:
>> import time
>> import importlib
>>
>> slist=[]
>>
>> file=input("What file should I read?")
>>
>> modules=[]
>>
>> f=open(file, "r")
>> data=f.readlines()
>> f.close()
> The standard way to write this is:
>
>      with open(file) as f:
>          data = f.readlines()
>
> or (giving that iterating a text file produces lines):
>
>      with open(file) as f:
>          data = list(f)
>
> but even more common is, since text files iterate lines:
>
>      with open(file) as f:
>          for x in f:
>
>> for x in data: # get the list of modules and remove any end of line for
>> x in data: # get the list of modules and remove any end of line
>> characters
>>      if(x.startswith ("import") or x.startswith("from")):
> This is a little loose, eg code like this:
>
>      imported_modules = []
>
> would match this test. Had you considered:
>
>      words = x.split()
>      if words and words[0] in ("import", "from"):
>
>>          if(word[1] not in modules):
>>              modules.append(word[1].strip("\n"))
> I'd assign the module name to a variable:
>
>      module_name = words[1]
>      if module_name not in modules:
>          modules.append(module_name)
>
> Your modules are a list. That involves a linear code to scan it.
> Admittedly, itis likely to be quite a short list, but a set works
> better. Earlier in the code:
>
>      modules = set()
>
> then the same test.
>
>      if module_name not in modules:
>          modules.add(module_name)
>
> But it looks like you're just accruing a unique collection of module
> names. Sets do that for free! So just:
>
>      modules.add(module_name)
>
> with no if-statement at all.
>
>> print("Found "+str(len(modules))+" modules.")
> print() converts its arguments to str for you. This is easier to write
> and read:
>
>      print("Found", len(modules), "modules.")
>
>> for x in modules:
>>      start=time.time()
>>      r=importlib.import_module(x)
> Not using "r"?
>
>>      if(time.time()==start): # probably cached
> This is dodgy. A slow system (particularly a slow hard drive) or a very
> high res time.time() function will fail this test.
>
>>          importlib.reload(r)
> You can inspect what's imported directly:
>
>      import sys
>      if module_name in sys.modules:
>          # already imported
>
> You can probably just delete things from there, too.
>
> What about:
>
>      if module_name in sys.modules:
>          del sys.modules[module_name]
>      start = time.time()
>      importlib.import_module(module_name)
>      end = time.time()
>      times[module_name] = end - start
>
> Then you can sort times.items() by name or time or whatever.
>
> At least brackets remove ambiguity.
>
> All the above intended as positive feedback.
>
> Cheers,
> Cameron Simpson <cs at cskk.id.au>
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-- 

Best Wishes,

Nathan Smith, BSC


My Website: https://nathantech.net