{
My thoughts as exhibited in a little Python script now have a name: Twining.
Unplanned illness slowed me down over the weekend, but the beauty of lambda expressions make transformations a breeze. I'll let the code document what I added.
cn = "Data Source=.\\sqlexpress;Initial Catalog=MVCBaby;Integrated Security=SSPI;"
mytrans = {"Field1":"upper","Field1": lambda x: x.upper(),"Field3": lambda x: x[::-1]}
database(cn).table("Photos").transform(mytrans).copyto.csv("c:\\foo.csv")
As you can see, "mytrans" is a dictionary containing a matching of column names to both a keyword string, "upper", and also lambda expressions that model functions to operate on the constituent data (the [::-1] idiom reverses a string). I'd add a few keywords for simple things people often do to data but the beauty of lambda expressions is that it keeps my code lazy and empowers whoever is using the script to make their own judgement about what to do with data.
Here's what goes on behind the scenes - the copyto class has a checkAndTransform method that matches up a field value with it's "transform":
def checkAndTransform(self, field, value):
if registrar.transforms.has_key(field):
if repr(type(registrar.transforms[field])) == "<type 'function'>":
value = registrar.transforms[field](value)
if registrar.transforms[field] == "upper":
value = value.upper()
return value
I'm not Pythonic enough yet to know if I need to call repr and do a string comparison when testing if a type is a function, but it works just fine.
So a few thoughts:
1. What are the usual changes we make to data when exporting or importing?
2. Is it stupid to have shortcut strings or should I just fall back on writing lambdas?
3. Is there a better way of testing for a function than
repr(type(registrar.transforms[field])) == "<type 'function'>"
The to-do list from my previous post is still intact, I'll be working through it in the near future. Have a look at the complete script and if you have thoughts or opinions, please let me know. A big goal here is not only to make something useful, but to learn Python (and be Pythonic, the two don't necessarily coincide).
Here's a full list of what can be done at this point:
mytrans = {"Field1":"upper","Field2": lambda x: x.upper(),"Field3": lambda x: x[::-1]}
database(cn).table("MyTable").transform(mytrans).copyto.csv("c:\\foo.csv") #with transform
database(cn).table("MyTable").copyto.csv("c:\\foo.csv") #without transform
database(cn).table("MyTable").copyto.database(cn2)
database(cn).table("MyTable").copyto.xmlFieldsAsAttributes("c:\\here.xml")
database(cn).table("MyTable").copyto.xmlFieldsAsElements("c:\\there.xml")
database(cn).backupto("C:\\temp\\my_backup.bak")
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