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How To Call Function Dynamically
I have a class containing several lists as attributes and several add methods to append an object to a specific list based on its type.
My code reads a csv file containing the type of an object in order to create and add it to my cart.
My problem is that I'm testing the object type to call the right 'add' function using if elif
syntax but this is not very nice and hard to maintain.
For example
import csv
class my_item():
def __init__(self, name):
self.name = name
class fruit(my_item):
pass
class vegetable(my_item):
pass
class meat(my_item):
pass
class fish(my_item):
pass
class shopping_cart():
def __init__(self):
self.fruits = []
self.vegetables = []
self.meat = []
self.fish = []
def add_fruit(self, o):
self.fruits.append(o)
def add_vegetable(self, o):
self.vegetables.append(o)
def add_meat(self, o):
self.meat.append(o)
def add_fish(self, o):
self.fish.append(o)
def __str__(self):
msg = ""
msg += "{:<25}= {:<5}\n".format('Total', str(len(self.fruits) + len(self.vegetables) + len(self.meat) + len(self.fish)))
for attrname in vars(self):
value = getattr(self, attrname)
if isinstance(value, list):
msg += " {:<23}= {:<5}\n".format(attrname, len(value))
return msg
def main():
input_f = 'input.csv'
my_cart = shopping_cart()
with open(input_f, 'r') as i:
rows = csv.reader(i, delimiter=';')
for row in rows:
item = globals()[row[0]](row[1])
if item.__class__.__name__ == 'fruit':
my_cart.add_fruit(item)
elif item.__class__.__name__ == 'vegetable':
my_cart.add_vegetable(item)
elif item.__class__.__name__ == 'meat':
my_cart.add_meat(item)
else:
my_cart.add_fish(item)
print (my_cart)
if __name__ == '__main__':
main()
Do you see any alternatives to the if elif
block?
Thanks for your feedback.
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Answer
Sure, you just need to create the function name dynamically and call it.
Be careful, this will works only if my_cart have add_{{ item name }}
method.
def main():
input_f = 'input.csv'
my_cart = shopping_cart()
with open(input_f, 'r') as i:
rows = csv.reader(i, delimiter=';')
for row in rows:
item = globals()[row[0]](row[1])
item_name = item.__class__.__name__
item_add_func_name = 'add_{}'.format(item_name)
item_add_func = getattr(my_cart, item_add_func_name, None)
if item_add_func and callable(item_add_func):
item_add_func(item)
# if item.__class__.__name__ == 'fruit':
# my_cart.add_fruit(item)
# elif item.__class__.__name__ == 'vegetable':
# my_cart.add_vegetable(item)
# elif item.__class__.__name__ == 'meat':
# my_cart.add_meat(item)
# else:
# my_cart.add_fish(item)
print (my_cart)
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source: stackoverflow.com
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