Which of these is pythonic? and Pythonic vs. Speed
- by Kashyap Nadig
Hi!
I'm new to python and just wrote this module level function:
def _interval(patt):
""" Converts a string pattern of the form '1y 42d 14h56m'
to a timedelta object.
y - years (365 days), M - months (30 days), w - weeks, d - days,
h - hours, m - minutes, s - seconds"""
m = _re.findall(r'([+-]?\d*(?:\.\d+)?)([yMwdhms])', patt)
args = {'weeks': 0.0,
'days': 0.0,
'hours': 0.0,
'minutes': 0.0,
'seconds': 0.0}
for (n,q) in m:
if q=='y':
args['days'] += float(n)*365
elif q=='M':
args['days'] += float(n)*30
elif q=='w':
args['weeks'] += float(n)
elif q=='d':
args['days'] += float(n)
elif q=='h':
args['hours'] += float(n)
elif q=='m':
args['minutes'] += float(n)
elif q=='s':
args['seconds'] += float(n)
return _dt.timedelta(**args)
My issue is with the for loop here i.e the long if elif block, and was wondering if there is a more pythonic way of doing it.
So I re-wrote the function as:
def _interval2(patt):
m = _re.findall(r'([+-]?\d*(?:\.\d+)?)([yMwdhms])', patt)
args = {'weeks': 0.0,
'days': 0.0,
'hours': 0.0,
'minutes': 0.0,
'seconds': 0.0}
argsmap = {'y': ('days', lambda x: float(x)*365),
'M': ('days', lambda x: float(x)*30),
'w': ('weeks', lambda x: float(x)),
'd': ('days', lambda x: float(x)),
'h': ('hours', lambda x: float(x)),
'm': ('minutes', lambda x: float(x)),
's': ('seconds', lambda x: float(x))}
for (n,q) in m:
args[argsmap[q][0]] += argsmap[q][1](n)
return _dt.timedelta(**args)
I tested the execution times of both the codes using timeit module and found that the second one took about 5-6 seconds longer (for the default number of repeats).
So my question is:
1. Which code is considered more pythonic?
2. Is there still a more pythonic was of writing this function?
3. What about the trade-offs between pythonicity and other aspects (like speed in this case) of programming?
p.s. I kinda have an OCD for elegant code.
EDITED _interval2 after seeing this answer:
argsmap = {'y': ('days', 365),
'M': ('days', 30),
'w': ('weeks', 1),
'd': ('days', 1),
'h': ('hours', 1),
'm': ('minutes', 1),
's': ('seconds', 1)}
for (n,q) in m:
args[argsmap[q][0]] += float(n)*argsmap[q][1]
