List Comprehensions With Class Objects

I have a class named StrucData in subfile.py class StrucData: def __init__(self, name): self.name=name def loadData(self, size=1, cost=1): self.size=size self.cost

Solution 1:

Complementing Bill Huang's response, if you're not free to change the object and you don't want to iterate twice, you could add a helper function:

def load_data(idx, size, cost):
    result = StructData(idx)
    result.loadData(size, cost)
    return result

[load_data(x, size=3, cost=4) for x in range(3)]

As a side-note, if you don't really need the instance to have the name and loadData separated, you could just use a namedtuple:

from collections import namedtuple

StructData = namedtuple('StructData', ['name', 'size', 'cost'])
print([StructData(name=x, size=3, cost=4) for x in range(3)])

Wich would return:

[StructData(name=0, size=3, cost=4), 
 StructData(name=1, size=3, cost=4), 
 StructData(name=2, size=3, cost=4)]

Finally, seeing that you have names such as "data1", "data2", you might want to have that as classnames, you can do so with namedtuple as long as names are valid class identifiers:

from collections import namedtuple

list_index = ['data1', 'data2', 'data3']
print([namedtuple(name, ['size', 'cost'])(3, 4) for name in list_index])

Result:

[data1(size=3, cost=4), data2(size=3, cost=4), data3(size=3, cost=4)]

Solution 2:

If you are free to append return self to the last line of StrucData.loadData() within subfile.py, it could be simplified like this:

# in the main file
listObjects = [StrucData(idx).loadData(size=3, cost=4) for idx in listIndex]

Otherwise, you have to do this separately because loadData() won't return anything for a list comprehension expression.

listObjects = [StrucData(idx) for idx in listIndex]
for i in range(3):
    listObjects[i].loadData(size=3, cost=4)