Re: [Tutor] Merge a dictionary into a string

[Mats Wichmann]

On 3/16/19 11:39 AM, Valerio Pachera wrote:
> Consider this:
> 
> import collections
> d = OrderedDict(a='hallo', b='world')
> 
> I wish to get a single string like this:
> 
> 'a "hallo" b "world"'
> 
> Notice I wish the double quote to be part of the string.
> In other words I want to wrap the value of a and b.

So the question that comes to mind is "why"?  I don't mean that in the
negative sense as in you don't want to do that, but your use case may
drive the choice of possible solutions.

For example, I once got asked very nearly this question by someone who
it turned out wanted to serialize the dict into something that could
later be used to load up a dict. String is what he thought of, but in
this case json, or pickle, turned out to be a better solution for what
he wanted than a string.

If you only want to print the string for informational purposes, the
suggestions here will work well.  You can even define your own class
which inherits from OrderedDict and just provides a new definition of
the method which produces a string representation and gives you what you
want without calling anything, like this:

>>> class MyOrderedDict(OrderedDict):
... def __repr__(self):
... return " ".join(f'{k} "{v}"' for k, v in self.items())
...
>>>
>>> d = MyOrderedDict(a='hallo', b='world')
>>> print(d)
a "hallo" b "world"
>>> x = str(d)
>>> x
'a "hallo" b "world"'


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Re: [Tutor] Merge a dictionary into a string

[David L Neil]

On 18/03/19 6:05 AM, Mats Wichmann wrote:

On 3/16/19 11:39 AM, Valerio Pachera wrote:

Consider this:
import collections
d = OrderedDict(a='hallo', b='world')
I wish to get a single string like this:
'a "hallo" b "world"'
Notice I wish the double quote to be part of the string.
In other words I want to wrap the value of a and b.



So the question that comes to mind is "why"?  I don't mean that in the
negative sense as in you don't want to do that, but your use case may
drive the choice of possible solutions.


Reading the OP, I immediately recognised the problem - meantime others 
had responded and the f'string' suggestion seemed most apropos.



Somewhat intrigued, and to answer the use-case question, I went looking 
in my personal collection of RDBMS routines and "snippets" (which have 
hardly been updated since Py2, excepting (IIRC) when MySQL's 
Connector-Python extended into dictionary-cursors).


The Connector will automatically delimit field/colNMs passed within a 
variable collection ('escaping' practice, highly recommended!) - a 
SELECT clause (for example). However, such automation is not applied to 
similar appearing in other clauses.


One of my helper-routines creates a comma-separated string by first 
surrounding columnNMs with back-ticks and then .join()ing. It's not 
rocket-surgery, but has been handy and import-ed many, many times.


YAGNI: me being me [puffs-out chest in a most unattractive fashion], one 
of the function's optional arguments offers a choice of delimiter. Can't 
recall ever using it 'elsewhere' though.



Thanks to the OP, and respondents making me think.
Have added to my >=v3.6 Backlog...
--
Regards =dn
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