String formatting using dictionaries

[Clodoaldo Pinto]

I know how to format strings using a dictionary:

d = {'list':[0, 1]}
'%(list)s' % d

'[0, 1]'

Is it possible to reference an item in the list d['list']?:

'%(list[0])s' % d

Traceback (most recent call last):
File "<stdin>", line 1, in ?
KeyError: 'list[0]'

Regards, Clodoaldo Pinto

 

[Fredrik Lundh]

I know how to format strings using a dictionary:

d = {'list':[0, 1]}
'%(list)s' % d

'[0, 1]'

Is it possible to reference an item in the list d['list']?:

'%(list[0])s' % d

Traceback (most recent call last):
File "<stdin>", line 1, in ?
KeyError: 'list[0]'

not directly, but you can wrap the dictionary in a custom mapper
class:

class mapper(dict):
def __getitem__(self, key):
try:
return dict.__getitem__(self, key)
except KeyError:
k, i = key.split("[")
i = int(i[:-1])
return dict.__getitem__(self, k)

>>> d = {"list": [0, 1]}
>>> d = mapper(d)
>>> '%(list)s' % d [0, 1]
>>> '%(list[0])s' % d

0

</F>

 

[Peter Otten]

I know how to format strings using a dictionary:

d = {'list':[0, 1]}
'%(list)s' % d

'[0, 1]'

Is it possible to reference an item in the list d['list']?:

'%(list[0])s' % d

Traceback (most recent call last):
File "<stdin>", line 1, in ?
KeyError: 'list[0]'

No, but you can provide a modified dictionary to get the effect:
.... def __getitem__(self, key):
.... if key in self:
.... return super(Dict, self).__getitem__(key)
.... return eval(key, self)
....

d = Dict(list=[0, 1])
"%(list)s" % d '[0, 1]'
"%(list[0])s" % d '0'
"%(list[1]+42)s" % d

'43'

Peter

 

[Clodoaldo Pinto]

Thank you guys, you are great!