using python map to apply type func in tuple to a list of strings

Question

I have a list d of 'tokens' all strings and a list of tuples of the form (fieldname,fieldtype) For Example

ds = ['1','1','1','1','1']
fs = [('type',str),('value',int),('hidden',bool),('length',int),('pieces',str)

and I want to make a dict v having the following form

v = {'type':'1','value',1,'hidden':True,'length':1,'pieces','1')

What I currently have is very inefficient (I map the type func in the tuple to elements in the list one at a time)

v = {}
for j in xrange(len(fs)):
    v[fs[j]] = map(fs[j][1],[ds[j]])[0]

How can I make this efficient and easy to read? I've tried lambdas, etc. If this were a one time thing I would just do it manually but there are multiple lists of tuples some of them 50 elements long.

Thanks all for below answers so promptly

WraithWireless
– WraithWireless

2014-04-17 17:17:49 +00:00
Commented Apr 17, 2014 at 17:17 — WraithWireless
– WraithWireless, Commented Apr 17, 2014 at 17:17

alecxe · Accepted Answer · 2014-04-17 13:32:27Z

4

You can zip() the lists and apply function defined in fs to the appropriate ds value:

>>> ds = ['1','1','1','1','1']
>>> fs = [('type',str),('value',int),('hidden',bool),('length',int),('pieces',str)]
>>> {key: f(value) for (key, f), value in zip(fs, ds)}
{'hidden': True, 'type': '1', 'length': 1, 'value': 1, 'pieces': '1'}

answered Apr 17, 2014 at 13:32

alecxe

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anon582847382 · Accepted Answer · 2014-04-17 13:41:24Z

1

I was thinking something along the lines of:

>>> items = iter(ds)
>>> v = {a: b(next(items)) for a, b in fs}
>>> v
{'type': '1', 'hidden': True, 'pieces': '1', 'length': 1, 'value': 1}

That is what I would probably do.

edited Apr 17, 2014 at 13:41

answered Apr 17, 2014 at 13:34

anon582847382

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2 Comments

WraithWireless Over a year ago

used as it seems most efficient, never even thought of a dict comprehension.

anon582847382 Over a year ago

@dvp It is most efficient as you are only holding one item in memory at a time, but with zip you iterate twice unnecessarily. Glad I could help!

mshsayem · Accepted Answer · 2014-04-17 13:35:31Z

0

My idea (not much readable):

>>> v = {t[0]:t[1](ds[i]) for i,t in enumerate(fs)}
>>> v
{'hidden': True, 'type': '1', 'length': 1, 'value': 1, 'pieces': '1'}

answered Apr 17, 2014 at 13:35

mshsayem

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