class Cust(object):
def __init__(self,cust_id,cust_day,cust_amt):
self.id=cust_id
self.total=0
self.days=[cust_day]
self.amounts=[cust_amt]
def add_Purchases(self,day,amount):
self.amounts.append(amount)
self.days.append(day)
print("add Purchase Executed for ",self.id,self.amounts)
print(self.get_Total_Sales())
def get_Total_Sales(self):
total = sum(self.amounts)
return total
class DB(object):
def __init__(self,filedir):
self.dir=filedir
self.DB_cust={}
self.createDatabase(filedir)
def importFile(self,file):
file.readline()
for line in file:
val=line.split(",")
customerID=data[0]
if customerID in self.DB_cust:
self.DB_cust[customerID].add_Purchases(val[2],float(val[3]))
else:
self.DB_cust[customerID]=Cust(val[0],val[1],val[2],float(val[3]))
I am trying to get the ID for maximum value of total. I call get_total_sales() from the instance method in DB class get_Max_ID()
def get_Max_ID(self):
print("Max Sale ID here")
Cust.get_Total_Sales()
This obviously results in
TypeError: get_Total_Sales() missing 1 required positional argument: 'self'
If I pass self through get_Max_ID. It would pass the self of DB and not Cust. I am not sure how to pass the self of Cust whilst calling it from DB class.
Clarification - The get_Total_Sales() gets the total for each customer but I am trying to get maximum value of total out of all the customer instances. (I have not written that part of code which draws maximum total)
Going by what OP says they want to do in the question comments, they probably want something like:
max([cust.get_Total_Sales() for id, cust in self.DB_cust.items()])
It will iterate over the dictionary of customers, and for each pair key/value pair (id and cust) will call and return that Cust's get_Total_Sales().
Then max will take all the individual results from the generated list of values and return only the maximum value.
As asked in the comment, although I see no reason not to use a comprehension:
results = []
for id, cust in self.DB_cust.items():
results.append(cust.get_Total_Sales())
return max(results)
Related
I need to be able to implement dictionaries into this code. Not all needs to be changed just were i can change it and it still does the same job.
In a test file I have a list of three strings (1, once),(2,twice).(2, twice).
I'm guessing the number will represent the value.
This code passes the tests but I am struggling to understand how I can use dictionaries to make it do the same job.
If any one can help it'll be grateful.
The current is:
The list items are in a test file elsewhere.
class Bag:
def __init__(self):
"""Create a new empty bag."""
self.items = []
def add(self, item):
"""Add one copy of item to the bag. Multiple copies are allowed."""
self.items.append(item)
def count(self, item):
"""Return the number of copies of item in the bag.
Return zero if the item doesn't occur in the bag.
"""
counter = 0
for an_item in self.items:
if an_item == item:
counter += 1
return counter
def clear(self, item):
"""Remove all copies of item from the bag.
Do nothing if the item doesn't occur in the bag.
"""
index = 0
while index < len(self.items):
if self.items[index] == item:
self.items.pop(index)
else:
index += 1
def size(self):
"""Return the total number of copies of all items in the bag."""
return len(self.items)
def ordered(self):
"""Return the items by decreasing number of copies.
Return a list of (count, item) pairs.
"""
result = set()
for item in self.items:
result.add((self.count(item), item))
return sorted(result, reverse=True)
I have been scratching my head over it for a while now. I can only use these also for dictionaries.
Items[key] = value
len(items)
dict()
items[key]
key in items
Del items[key]
Thank you
Start with the simplest possible problem. You have an empty bag:
self.items = {}
and now a caller is trying to add an item, with bag.add('twice').
Where shall we put the item?
Well, we're going to need some unique index.
Hmmm, different every time, different every time, what changes with each .add()?
Right, that's it, use the length!
n = len(self.items)
self.items[n] = new_item
So items[0] = 'twice'.
Now, does this still work after a 2nd call?
Yes. items[1] = 'twice'.
Following this approach you should be able to refactor the other methods to use the new scheme.
Use unit tests, or debug statements like print('after clear() items is: ', self.items), to help you figure out if the Right Thing happened.
Here I created a module.
class Employee:
def __init__(self):
self.name = input("Enter your name: ")
self.account_number = int(input("Enter your account number: "))
def withdraw(self): # it receives values from for
if withdraw1 > current_balance:
print ("You have entered a wrong number: ")
else:
print ("The current balance is: ", current_balance - withdraw1)
import TASK2 # I am importing the module I created
c = TASK2.Employee()
def for(self):
c.withdraw1 = int(input("enter number: "))
c.current_balance = int(input("Enter the current balance: "))
d = method(c.withdraw) # here I am trying to pass the values to withdraw
print (d)
The problem I get is that although it asks for the values instead of giving me an answer it gives me None.
Here's my take on your code.
# TASK2.py
class Employee:
def __init__(self):
self.name = input("Enter your name: ")
self.account_number = int(input("Enter your account number: "))
# make sure you initialise your member variables!
self.withdraw_val = 0 # withdraw1 is ambiguous, so I use withdraw_val instead
self.current_balance = 0
# receives values from for ### no it doesn't, right now, it GIVES values TO your "for" function
def withdraw(self):
if self.withdraw_val > self.current_balance: # remember to use "self." to
# access members within the class
print ("You have entered a wrong number: ")
else:
# again, remember "self."
print ("The current balance is: ", self.current_balance - self.withdraw_val)
# TASK2sub.py
import TASK2
c = TASK2.Employee()
def for_employee(employee): # (1) don't use "self" outside a class
# it's contextually unconventional
# (2) "for" is a keyword in Python, don't use it for naming
# variables/functions, it'll mess things up
employee.withdraw_val = int(input("Enter value to withdraw: "))
employee.current_balance = int(input("Enter the current balance: "))
return employee.withdraw_val # not entirely sure what you want to return
# but you should definitely return something
# if you're going to assign it to some variable
d = for_employee(c.withdraw()) # "for_employee" function needs a return statement
# ".withdraw()" method should also require a return statement
print(d)
Note: I'll be referring to your original for function as for_employee from now on. Also note that I'm still hazy about what you're trying to accomplish and that there is most probably a more suitable name for it.
Since your original for_employee function didn't return anything, it returns None by default. (This explains the output you saw.)
I think you're misunderstanding how functions work in general. For example,
d = for_employee(c.withdraw())
print(d)
Your comment for the .withdraw() method is inaccurate.
"it receives values from for"
More accurately, c.withdraw() will first be computed, then whatever it returns is passed into the for_employee function as a parameter. Instead of "receiving values from", the withdraw method "gives values to" the for_employee function.
Something more reasonable would be
c.withdraw() # on a line by itself, since it doesn't return anything
d = for_employee(c) # pass the entire object, since you'll be using self.withdraw_val and whatnot
print(d)
Another issue is with conventional naming. This is what I get from the IDLE (with Python 3.7) when defining a function named for
>>> def for(a): return a
SyntaxError: invalid syntax
Again, for is a keyword in Python, don't use it for naming your variables, functions, or classes.
With self, it's less severe (but I could see that it's confusing you). self is more of a convention used in class methods. But for_employee isn't a class method. So conventionally speaking, the parameter shouldn't be named self.
(I find the code spaghetti-ish, it might benefit if you refactor the code by moving the for_employee method into the class itself. Then it would completely make sense to use self.)
I am following "Fluent Python" to learn Function and Design Pattern:
In chapter 6 example-code/strategy.py
class Order: # the Context
def __init__(self, customer, cart, promotion=None):
self.customer = customer
self.cart = list(cart)
self.promotion = promotion
def total(self):
if not hasattr(self, '__total'):
self.__total = sum(item.total() for item in self.cart)
return self.__total
def due(self):
if self.promotion is None:
discount = 0
else:
discount = self.promotion(self) # <1>
return self.total() - discount
def __repr__(self):
fmt = '<Order total: {:.2f} due: {:.2f}>'
return fmt.format(self.total(), self.due())
I am very confused about:
def total(self):
if not hasattr(self, '__total'):
self.__total = sum(item.total() for item in self.cart)
return self.__total
What's the purpose of if condition here? I guess it could be more readable if:
def total(self):
return sum(item.total() for item in self.cart)
What's the key point I missed? could you please provide any hints?
What happens if you call total more than once? If self.cart hasn't changed, then you're needlessly recalculating the total, a potentially expensive operation.
You're checking if you've already stored the value. If you haven't you calculate it, but if you have you simply return the stored value without recalculating.
As an aside, I would expect name mangling to make your life difficult here because of the double underscore at the beginning of __total. You may want to consider switching to a single underscore.
I am currently taking some computer science courses in school and have come to a dead end and need a little help. Like the title says, I need of create a list of Class objects from a file with objects that have a duplicate not added to the list, I was able to successfully do this with a python set() but apparently that isn't allowed for this particular assignment, I have tried various other ways but can't seem to get it working without using a set. I believe the point of this assignment is comparing data structures in python and using the slowest method possible as it also has to be timed. my code using the set() will be provided.
import time
class Students:
def __init__(self, LName, FName, ssn, email, age):
self.LName = LName
self.FName = FName
self.ssn = ssn
self.email = email
self.age = age
def getssn(self):
return self.ssn
def main():
t1 = time.time()
f = open('InsertNames.txt', 'r')
studentlist = []
seen = set()
for line in f:
parsed = line.split(' ')
parsed = [i.strip() for i in parsed]
if parsed[2] not in seen:
studentlist.append(Students(parsed[0], parsed[1], parsed[2], parsed[3], parsed[4]))
seen.add(parsed[2])
else:
print(parsed[2], 'already in list, not added')
f.close()
print('final list length: ', len(studentlist))
t2 = time.time()
print('time = ', t2-t1)
main()
A note, that the only duplicates to be checked for are those of the .ssn attribute and the duplicate should not be added to the list. Is there a way to check what is already in the list by that specific attribute before adding it?
edit: Forgot to mention only 1 list allowed in memory.
You can write
if not any(s.ssn==parsed[2] for s in studentlist):
without committing to this comparison as the meaning of ==. At this level of work, you probably are expected to write out the loop and set a flag yourself rather than use a generator expression.
Since you already took the time to write a class representing a student and since ssn is a unique identifier for the instances, consider writing an __eq__ method for that class.
def __eq__(self, other):
return self.ssn == other.ssn
This will make your life easier when you want to compare two students, and in your case make a list (specifically not a set) of students.
Then your code would look something like:
with open('InsertNames.txt') as f:
for line in f:
student = Student(*line.strip().split())
if student not in student_list:
student_list.append(student)
Explanation
Opening a file with with statement makes your code more clean and
gives it the ability to handle errors and do cleanups correctly. And
since 'r' is a default for open it doesn't need to be there.
You should strip the line before splitting it just to handle some
edge cases but this is not obligatory.
split's default argument is ' ' so again it isn't necessary.
Just to clarify the meaning of this item is that the absence of a parameter make the split use whitespaces. It does not mean that a single space character is the default.
Creating the student before adding it to the list sounds like too
much overhead for this simple use but since there is only one
__init__ method called it is not that bad. The plus side of this
is that it makes the code more readable with the not in statement.
The in statement (and also not in of course) checks if the
object is in that list with the __eq__ method of that object.
Since you implemented that method it can check the in statement
for your Student class instances.
Only if the student doesn't exist in the list, it will be added.
One final thing, there is no creation of a list here other than the return value of split and the student_list you created.
I work with a csv data as follow:
ticker,exchange_country,company_name,price,exchange_rate,shares_outstanding,net_income
1,HK,CK HUTCHISON HOLDINGS LTD,1.404816984,7.757949829,3859.677979,31633
2,HK,CLP HOLDINGS LTD,1.312602194,7.757949829,2526.450928,16319
3,HK,HONG KONG & CHINA GAS CO LTD,0.234939214,7.757949829,12717.04199,7546.200195
11,HK,HANG SENG BANK LTD,2.198193203,7.757949829,1911.843018,15451
I have a StockStatRecord class:
class StockStatRecord:
def __init__(self, stock_load):
self.name = stock_load[0]
self.company_name = stock_load[2]
self.exchange_country = stock_load[1]
self.price = stock_load[3]
self.exchange_rate = stock_load[4]
self.shares_outstanding = stock_load[5]
self.net_income = stock_load[6]
How am I supposed to create another class to extract the data from that CSV, parse it, create new record and return the record created? In this class, it also needs to validate the rows when reading. Validation will fail for any row that is missing any piece of information, or if the name (symbol or player name) is empty, or if any of the numbers(int or float) cannot be parsed ( watch out of the division by zero).
There are several ways of doing this, either rolling out the code yourself, or using a Python module that is made for veryfing data-schemas, like Colander, or the extended CSV reader in Pandas (as Zwinck posted in the comment above).
What is not usually needed is a separate class to check values- you can do that on the same class - or usually, have a base class that implements the data-validation mechanisms, and then just have extra information on each field for the actual data classes. And finally, if you need to process data and spill an object back, there is no need for a class because in Python you can have functions independents of classes - there is no need to try to hammer down every piece of code to a class.
One simple thing to there is to (1) use Python's csv.DictReader instead of csv.Reader to read the rows - that way you have each piece of data bound to the column name already, as a dict, instead of a list where you have to manually track the column numbers, then set a property for each of the columns you need validation, so that the fields can be validated on setting - and a __init__ method that simply assigns all fields to their respectiv attributes:
class SockStatRecord:
def __init__(self, row):
for key, value in row.items():
setattr(self, key, value)
#property
def name(self):
return self._name
#name.setter
def name(self, value):
if not name: # example verification for empty name
raise ValueError
self._name = name
# continue for other fields
import csv
reader = csv.Dictreader(open("mydatafile.csv"))
all_records = []
for row in reader:
try:
all_records.append(StockDataRecord(row))
except ValueError:
print("Some error at record: {}".format(row))