tl;dr: My code "works", in that it gives me the answer I need. I just can't get it to stop running when it reaches that answer. I'm stuck with scrolling back through the output.
I'm a complete novice at programming/Python. In order to hone my skills, I decided to see if I could program my own "solver" for Implied Equity Risk Premium from Prof. Damodaran's Valuation class. Essentially, the code takes some inputs and "guesses and tests" a series of interest rates until it gets a "close" value to the input.
Right now my code spits out an output list, and I can scroll back through it to find the answer. It's correct. However, I cannot for the life of me get the code to "stop" at the correct value with the while function.
I have the following code:
per = int(input("Enter the # of periods forecast ->"))
divbb = float(input("Enter the initial dividend + buyback value ->"))
divgr = float(input("Enter the div + buyback growth rate ->"))
tbondr = float(input("Enter the T-Bond rate ->"))+0.000001
sp = int(input("Enter the S&P value->"))
total=0
pv=0
for i in range(1,10000):
erp = float(i/10000)
a = divbb
b = divgr
pv = 0
temppv = 0
print (sp-total, erp)
for i in range(0, per):
a=a * (1+b)
temppv = a / pow((1+erp),i)
pv=pv+temppv
lastterm=(a*1+tbondr)/((erp-tbondr)*pow(1+erp,per))
total=(pv+lastterm)
From his example, with the inputs:
per = 5
divbb = 69.46
divgr = 0.0527
tbondr = 0.0176
sp = 1430
By scrolling back through the output, I can see my code produces the correct minimum at epr=0.0755.
My question is: where do I stick the while to stop this code at that minimum? I've tried a lot of variations, but can't get it. What I'm looking for is, basically:
while (sp-total) > |1|, keep running the code.
per = 5
divbb = 69.46
divgr = 0.0527
tbondr = 0.0176
sp = 1430
total=0
pv=0
i = 1
while(abs(sp-total)) > 1:
erp = i/10000.
a = divbb
b = divgr
pv = 0
temppv = 0
print (sp-total, erp)
for j in range(0, per):
a=a * (1+b)
temppv = a / pow((1+erp),j)
pv=pv+temppv
lastterm=(a*1+tbondr)/((erp-tbondr)*pow(1+erp,per))
total=(pv+lastterm)
i += 1
should work. Obviously, there are a million ways to do this. But the general gist here is that the while loop will stop as soon as it meets the condition. You could also test every time in the for loop and include a break statement, but because you don't know when it will stop, I think a while loop is better in this case.
Let me give you a quick rundown of two different ways you could solve a problem like this:
Using a while loop:
iterator = start value
while condition(iterator):
do some stuff
increment iterator
Using a for loop:
for i in xrange(startvalue, maxvalue):
do some stuff
if condition:
break
Two more thing: if you're doing large ranges, use the generator xrange. Also, it's probably a bad idea to reuse i inside your for loop.
I recommend CS101 from Udacity.com for learning Python. Also, if you're interested in algorithms, work through the problems at projecteuler.com
Related
I'm currently working on this problem that ask me to generate an arrow pattern using loops function that looks something like this:
"How many columns? 3"
*
*
*
*
*
I know I can do this with for loop(probably more efficient too), but that is not what I aimed for. I wanted to achieve this only using while loop.
I have some ideas:
1. I set up a control variable and an accumulator to control the loop
2. I then write 2 separate loops to generate the upper and lower part of the pattern. I was thinking about inserting the space before the asterisks using method like this:
(accumulator - (accumulator - integer)) * spaces.
#Ask the user how many column and direction of column
#they want to generate
Keep_going = True
Go = 0
while keep_going:
Column_num = int(input("How many columns? "))
if Column_num <= 0:
print("Invalid entry, try again!")
else:
print()
Go = 1
#Upper part
while Keep_going == True and Go == 1:
print("*")
print(""*(Column_num - (Column_num - 1) + "*")
...but I soon realized it wouldn't work because I don't know the user input and thus cannot manually calculate how many spaces to insert before asterisks. Now everything on the internet tells me to use for loop and range function, I could do that, but I think that is not helpful for me to learn python since I couldn't utilize loops very well yet and brute force it with some other method just not going to improve my skills.
I assume this is achievable only using while loop.
#Take your input in MyNumber
MyNumber = 5
i = 1
MyText = '\t*'
while i <=MyNumber:
print(MyText.expandtabs(i-1))
i = i+1
i = i-1
while i >=1:
print(MyText.expandtabs(i-1))
i = i-1
Python - While Loop
Well first you have to understand that a while loop loops until a requirement is met.
And looking at your situation, to determine the number of spaces before the * you should have an ongoing counter, a variable that counts how many spaces are needed before you continue. For example:
###Getting the number of columns###
while True:
number=int(input('Enter number of rows: '))
if number<=0:
print('Invalid')
else:
###Ending the loop###
break
#This will determine the number of spaces before a '*'
counter=0
#Loops until counter equals number
while counter!=number:
print(" "*counter + "*")
#Each time it loops the counter variable increases by 1
counter=counter+1
counter=counter-1
#Getting the second half of the arrow done
while counter!=0:
counter=counter-1
print(" "*counter + "*")
Please reply if this did not help you so that i can give a more detailed response
I'm just playing around with lists and have stumbled across an issue with my code. I can't figure out why my count() won't actually work and display the final total for the heads and tails. It prints 0 rather than what's in the new list..? I've tested the print newlist and it is showing that the list is updating once the loop has completed.
Can anyone help me fix this and explain what I am doing wrong?
Thanks!
import random
i = 0
spins = int(input ("How many spins do you want to do? "))
coin = ["heads", "tails"]
newList = []
while i < spins:
i = i+1
spin = random.sample(set(coin),1)
tallyCoin = spin
print (tallyCoin)
newList.append(tallyCoin)
if i >= spins:
print (newList)
totalHeads = newList.count("heads")
totalTails = newList.count("tails")
print ("the total heads for this round were: ", totalHeads)
print ("the total tails for this round were: ", totalTails)
random.sample returns a list so you are collecting lists with a single string in it instead of strings. Try random.sample(coin, 1)[0] instead.
I apologize as this is my first question on this site and it is extremely basic, but I am somewhat lost in a current lab I am trying to complete.
Currently I am attempting to count the amount of exchanges(Or swaps? Not sure on the right word there!) during a selection sort throughout the passes.
Now according to my current understanding, the replacement section of our formula is traversing my list. However, it doubles the amount of swaps it is actually supposed to be spitting back at me. Now this would lead me to believe an if statement might need to be operating in the outer loop, but that doesn't seem quite right to me.
An example of what I have done to cause this problem below. I am curious if I am on the right path or should I slash and burn or go back to the drawing board.
The reason I am counting them independently is I am displaying when there is a swap then a grand total of all the swaps. Which I find to be a bit ironic as with a selection sort you can only have 1 swap per pass?
Any case, I apologize for the rather basic question, but I seem to be missing something so I was hoping someone could point me in the right direction of if I should be focusing on the outer loop to determine the exchanges?
print( "Original list:" , a_list, "\n" )
count =1
n = len(a_list)
comp = n -1
exchanges=1
comp_total=0
exch_total=0
for end in range(n, 1, -1): # Each pass starts here
#Setting our running total to adjust for previous value.
comp_total +=comp-(count-1)
print("Pass", count, ":", "Comparisons:",comp-(count-1), "\tExchanges:", exchanges,"\n", end="\t ")
count += 1
# --- Search for Largest ---
min_position = 0
for i in range(1, end):
if a_list[i] > a_list[min_position]: # Perform n
min_position = i
exchanges = 0
exch_total +=1
else:
exchanges = 1
# --------------------------
temp = a_list [end - 1] # Perform exchange
a_list [end - 1] = a_list [min_position]
a_list [min_position] = temp
print(a_list)
print()
print("\tTotal Comparisons:",comp_total, "Total Exchanges:", exch_total)
selection_sort(a_list)
In this case,
My issue was the the fact my print statement was before the actual loop, this was throwing off my count, by placing the if statement past this point, I was able to get an accurate running total!
Cheers!
I'am beginner in programming and have struggled for a while with one task.
Want to write a program wich finds out how many iterations is needed to arrive at the number 6174 from the specified number.
For example.: if I take number 2341 and sort it.
1) 4321-1234=3087
2) 8730-378=8352
3) 8532-2358=6174 (in this case it`s needed 3 iterations.)
And I have to use ,,while loop,, that it runs a code until it comes to number 6174 and stops.
I wrote a code:
n =input('write for nummbers ')
n=str(n)
i=0
i+=1 #"i" show how many times iteration happend.
large = "".join(sorted(n, reverse=True))
little = "".join(sorted(n,))
n = int(large) - int(little)
print(n, i)
Can you give mee some hint how I could run it with while loop.
# untested, all bugs are free ;)
n = input('write for nummbers ')
n = int(n) # you need n as a number
i=0
while n != 6174:
i += 1 #"i" show how many times iteration happened.
large = "".join(sorted(str(n), reverse=True))
little = "".join(sorted(str(n),))
n = int(large) - int(little)
print(n, i)
http://www.cs.uni.edu/~diesburg/courses/cs1510_sp15/homework/PA04/index.htm
So I have this assignment. I have been trying to work out the code to find the additive and multiplicative roots of a user given input. I am new to python and know how to work the problem out, but without the tools (coding know how) have been just running in circles for quite a while now. So if anyone could be so kind as to help me figure out the coding. I have tried slicing the list, but keep getting an error if I try to make the string an int and if I leave it as an string it just doesn't seem to run. I know there is probably a way using modulous as well, but have yet to quite master it.
Thank you for any help any of you are able to leave me.
Edit
Here is the code I have so far.
import sys
userStr = input("What number should I use for my \
calculations? ")
userInt = int (userStr)
original = userStr #Save Copy of original value
originalTwo = userStr #Save second Copy of original value
addCount = 0
mulCount = 0
#Stop the program if the integer is less than or equal to 0
while userInt <= 0:
print ("Thanks for playing along!")
sys.exit()
#Use a while loop to repeat the process of splitting an integer into single digits and then adding the individual digits.
print = ("Addition")
while userInt > 9:
userInt = sum(map(int, userStr))
print("New Value: ",userStr)
addCount = addCount + 1
#Use a while loop to repeat the process of splitting an integer into single digits and then multiplying the individual digits.
print = ("Multiplication")
while original > 9:
original = (map (int, original))
print("New Value: ",original)
mulCount = mulCount + 1
#Print the outputs to the screen for the user.
print("For the Integer: ",userInt)
print(" Additive Persistence= ",addCount,", Additive Root= ", userInt)
print(" Multiplicative Persistence= ",mulCount,",
Multiplicative Root= ", original)