python chaining

Updated

Let's say I have:

dic={"z":"zv", "a":"av"}
##开发者_如何转开发 why doesn't the following return a sorted list of keys?
keys=dic.keys().sort()

I know I could do the following and have the proper result:

dic={"z":"zv", "a":"av"}
keys=dic.keys()
skeys=keys.sort()  ### skeys will be None

Why doesn't the first example work?

.sort doesn't return the list. You could do:

keys = sorted(dic.keys())

sort() modifies the contents of the existing list. it doesn't return a list. See the manual.