Python dict to user format string

Question

What is the easiest way to convert Python dict e.g.:

a = {'a': 'value', 'b': 'another_value', ...}

into string using user format e.g.:

'%s - %s\n'

so it gives me:

a - value
b - another_value

This works, but maybe there is something shorter/better using map (without iterating over collection)

''.join(['%s %s\n' % o for o in a.items()])

There's no need for that list, just do: '\n'.join('%s %s' % o for o in a.items()) — Rik Poggi
– Rik Poggi, Commented Jan 17, 2012 at 11:56
map still iterates over the collection, it just happens that sometimes it is faster and sometimes slower than an explicit loop. — Duncan
– Duncan, Commented Jan 17, 2012 at 13:23

Roman Bodnarchuk · Accepted Answer · 2012-01-17 11:54:50Z

5

I'd write this as:

>>> print '\n'.join(' '.join(o) for o in a.items())
a value
b another_value

Or:

>>> print '\n'.join(map(' '.join, a.items()))
a value
b another_value

answered Jan 17, 2012 at 11:54

Roman Bodnarchuk

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2 Comments

NPE Over a year ago

I may be reading the question wrong, but to me "using user format" suggests that the format string is essentially a parameter.

marcinpz Over a year ago

YES. Joining string is a parameter, so I could create function def dict_to_str(dict_obj, join_str_format)

NPE · Accepted Answer · 2012-01-17 11:55:36Z

2

You can omit the square brackets to avoid building the intermediate list:

''.join('%s %s\n' % o for o in a.items())

Since you're asking about map, here is one way to write it using map:

''.join(map(lambda o:'%s %s\n' % o, a.items()))

It's a matter of preference, but I personally find it harder to read than the original version.

answered Jan 17, 2012 at 11:55

NPE

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2 Comments

Duncan Over a year ago

map when using lambda is almost certainly slower than just using for. Of course you can avoid the lambda here but then it is definitely harder to read: ''.join(map('%s %s\n'.__mod__, a.items()))

marcinpz Over a year ago

I just thought there is shorter version without iterating over list, but I see this first version is simply what I need :) Thank You.

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