My code is as follow for the budget app thus far. I could not get it to update the transfer from in another object and I don’t understand what is wrong with how I am calling the other object’s deposit method.
class Category:
CategoryName = ""
Ledger = []
def __init__(self, name, ledger=[]):
self.CategoryName = name
self.Ledger = ledger
def deposit (self, amount, description =""):
self.Ledger.append([amount , description])
def withdraw (self, amount, description = ''):
if self.check_funds(amount):
self.Ledger. append([0 - amount, description])
else:
pass
def get_balance (self):
t = 0
for i in range (len(self.Ledger)):
t = t + self.Ledger[i][0]
return t
def check_funds (self, amount):
if amount > self.get_balance():
return False
else:
return True
def transfer (self, amount, Other_cat):
if self.check_funds(amount):
Transfer_to = "Transfer to " + Other_cat.CategoryName
self.Ledger.append([0 - amount, Transfer_to])
Transfer_from = "Transfer from " + self.CategoryName
Other_cat.deposit(amount, Transfer_from)
return True
else:
return False
def create_spend_chart(categories):
pass
Appreciate your help in pointing out my mistake.
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I’m not sure if I understand what issue you are having. Can you write what you expect to be happening and what is happening instead? Are you getting any error?
def transfer (self, amount, Other_cat):
if self.check_funds(amount):
Transfer_to = "Transfer to " + Other_cat.CategoryName
self.Ledger.append([0 - amount, Transfer_to])
Transfer_from = "Transfer from " + self.CategoryName
Other_cat.deposit(amount, Transfer_from)
return True
else:
return False
def transfer (self, amount, Other_cat):
if self.check_funds(amount):
Transfer_to = "Transfer to " + Other_cat.CategoryName
self.Ledger.append([0 - amount, Transfer_to])
Transfer_from = "Transfer from " + self.CategoryName
Other_cat.deposit(amount, Transfer_from)
print (self.Ledger)
print (Other_cat.Ledger)
return True
else:
return False
I expect to print the amount transferred from the “Food” ledger to the “Clothing” ledger but when I added a print statement to the end “print (self.Ledger)” had both (-50, transfer to clothing) and (50, transfer from food) in the same ledger. When i print “print (Other_cat.Ledger)”, it also had both records and I don’t understand why.
Python evaluates default parameters in functions and methods just once. As list is a mutable data type, what this basically means is, in case when ledger is not passed when class instance is created, the same list will be used for every such instance.
To avoid such behavior something like this can be used:
def func(default=None):
if default is None:
default = []
And one slightly unrelated tip - CategoryName and Ledger don’t need to be defined below class as class variables. Their presence there may result in some unexpected behavior. Defining them in __init__ as instance variables preceded with self. is enough for what they are used in here.
