function vs lambda statement

Question

Lambda is confusing me a little, here is what I've got :

lmb = lambda d: datetime.datetime.strptime(d["Date[G]"]+"-"+d["Time[G]"], "%d-%b-%Y-%H:%M:%S.%f")

if I write a function like this :

def time(d):
    t = datetime.datetime.strptime(d["Date[G]"]+"-"+d["Time[G]"], "%d-%b-%Y-%H:%M:%S.%f")
    return t.strftime("%d-%b-%Y-%H")

I can return t.strftime("%d-%b-%Y-%H").

Can I embed a somethine like t.strftime("%d-%b-%Y-%H") in my lambda statement ?

EDIT

I`ve tried this :

lmb = lambda d: datetime.datetime.strptime(d["Date[G]"]+"-"+d["Time[G]"], "%d-%b-%Y-%H:%M:%S.%f").strftime("%d-%b-%Y-%H")

but it returns :

AttributeError: 'str' object has no attribute 'strftime'

which doesn't happen using the function ..

Winston Ewert · Accepted Answer · 2012-05-01 03:16:55Z

3

Sure:

lmb = lambda d: datetime.datetime.strptime(d["Date[G]"]+"-"+d["Time[G]"], "%d-%b-%Y-`%H:%M:%S.%f").strftime("%d-%b-%Y-%H")

But it pretty quickly just makes sense to use a function.

answered May 1, 2012 at 3:16

Winston Ewert

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2 Comments

Finger twist Over a year ago

I could use a function but I`m using the lambda statement this way : for k, g in itertools.groupby(csvReader, key = lmb)

Winston Ewert Over a year ago

@Fingertwist I copied/pasted your new version, and I don't get the error. You can pass the function to groupby, functions and lambda are the exact same thing.

srgerg · Accepted Answer · 2012-05-01 03:16:45Z

3

Yes, you can do it like this:

lmb = lambda d: datetime.datetime.strptime(d["Date[G]"]+"-"+d["Time[G]"], "%d-%b-%Y-%H:%M:%S.%f").strftime("%d-%b-%Y-%H")

I tested this on Python 2.7:

>>> lmb = lambda d: datetime.datetime.strptime(d["Date[G]"]+"-"+d["Time[G]"], "%d-%b-%Y-%H:%M:%S.%f").strftime("%d-%b-%Y-%H")
>>> lmb({"Date[G]": "22-Apr-2012", "Time[G]": "07:23:24.123"})
'22-Apr-2012-07'

answered May 1, 2012 at 3:16

srgerg

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