Convert month name to month number faster

jfabiani at yolo.com jfabiani at yolo.com
Wed Jan 6 15:43:29 CET 2010


VYAS ASHISH M-NTB837 wrote:

>  
> How about using list.index() and storing month names in a list? You may
> want to measure performance your self and conclude.
> 
> Regards,
> Ashish Vyas
> 
> -----Original Message-----
> From: python-list-bounces+ntb837=motorola.com at python.org
> [mailto:python-list-bounces+ntb837=motorola.com at python.org] On Behalf Of
> wiso
> Sent: Wednesday, January 06, 2010 4:34 PM
> To: python-list at python.org
> Subject: Convert month name to month number faster
> 
> I'm optimizing the inner most loop of my script. I need to convert month
> name to month number. I'm using python 2.6 on linux x64.
> 
> 
> month_dict = {"Jan":1,"Feb":2,"Mar":3,"Apr":4, "May":5, "Jun":6,
> "Jul":7,"Aug":8,"Sep":9,"Oct":10,"Nov":11,"Dec":12}
> 
> def to_dict(name):
>   return month_dict[name]
> 
> def to_if(name):
>     if name == "Jan": return 1
>     elif name == "Feb": return 2
>     elif name == "Mar": return 3
>     elif name == "Apr": return 4
>     elif name == "May": return 5
>     elif name == "Jun": return 6
>     elif name == "Jul": return 7
>     elif name == "Aug": return 8
>     elif name == "Sep": return 9
>     elif name == "Oct": return 10
>     elif name == "Nov": return 11
>     elif name == "Dec": return 12
>     else: raise ValueError
> 
> import random
> l = [random.choice(month_dict.keys()) for _ in range(1000000)]
> 
> from time import time
> t = time(); xxx=map(to_dict,l); print time() - t # 0.5
> t = time(); xxx=map(to_if,l); print time() - t   # 1.0
> 
> 
> is there a faster solution? Maybe something with str.translate?
> 
> The problem is a little different because I don't read random data, but
> sorted data. For example:
> 
> l = [x for x in
> ("Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"
> )
> for _ in range(1000)] # ["Jan","Jan", ..., "Feb", "Feb", ...]
> 
> so maybe the to_if approach will be faster if I write the case in the
> best
> order. Look:
> 
> l = ["Jan"] * 1000000 # to_if is in the best order for "Jan"
> t = time(); xxx=map(to_dict,l); print time() - t # 0.5
> t = time(); xxx=map(to_if,l); print time() - t # 0.5
> 
> 
what just using 
get(key[, default])¶
    Return the value for key if key is in the dictionary, else default. If
default is not given, it defaults to None, so that this method never raises
a KeyError.



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