How can i implement nested loop in list comprehension

Question

Currently i have this

def convert_tuple(self, listobj, fields=None):
    return [(obj.start, obj.end) for obj in listobj]

But i have hard coded the fields.

I want to have fields as another list like

def convert_tuple(self, listobj, fields=['start', 'end', 'user']):
    return [(obj.field) for obj in listobj for field in fields]

How can i implement that

Expected output

[('2am', '5am', 'john'), ('3am', '5am', 'john1'), ('3am', '5am', 'john2') ]

where 2am is start , 5am is end , john is username

Example input with desired output would be helpful.

Ryne Everett
– Ryne Everett

2015-05-30 04:22:23 +00:00
Commented May 30, 2015 at 4:22 — Ryne Everett
– Ryne Everett, Commented May 30, 2015 at 4:22

Abhijit · Accepted Answer · 2015-05-30 04:23:17Z

2

You can leverage python builtin getattr along with nested list comprehension to achieve what you are envisaging.

def convert_tuple(self, listobj, fields=['start', 'end', 'user']):
    return [(getattr(obj, field) for  field in fields)
            for obj in listobj]

It is worth noting that your comprehension is rather a cartesian product rather than a nested comprehension

answered May 30, 2015 at 4:23

Abhijit

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user3214546 Over a year ago

How can i display it properly currently i get [genexpres, genexpression] , i want to expand it

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