I want to format a string and be able to use the dot operator, so that I can construct template strings containing eg {user.name}
, {product.price}
.
I tried this:
'Hello {user.name}'.format( {'user': { 'name': 'Markus' } } )
KeyError: 'user'
'Hello {user.name}'.format( **{'user': { 'name': 'Markus' } } )
AttributeError: 'dict' object has no attribute 'name'
Is there a way to do it?
Python dict
objects are unfortunately not attribute accessible (ie with the dot notation) by default. So you can either resign yourself to the uglier brackets notation:
'Hello {user[name]}'.format( **{'user': { 'name': 'Markus' } } )
Or you can wrap your data in a dot-accessible object. There are a handful of attribute-accessible dictionary classes you can install from PyPI , such as stuf .
from stuf import stuf
'Hello {user.name}'.format( **stuf({'user': { 'name': 'Markus' } }) )
I tend to keep my collections in stuf
objects so that I can easily access them by attribute.
The minimal change is to use square brackets in your template, rather than a period:
# v Note
>>> 'Hello {user[name]}'.format(**{'user': {'name': 'Markus'}})
'Hello Markus'
Alternatively, put objects that actually have that attribute in the dictionary, eg a custom class or collections.namedtuple
:
>>> class User(object):
def __init__(self, name):
self.name = name
>>> 'Hello {user.name}'.format(**{'user': User('Markus')})
'Hello Markus'
Note also that if you're writing out the literal you can just use a keyword argument:
>>> 'Hello {user.name}'.format(user=User('Markus'))
'Hello Markus'
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