I have a set of numbers which is generated real-time during running the code. In the snippet of code shown below with the function constant_set, the number generated real time are stored in the variable set_accepted_list_frozen. What i want to ask is, if i want to keep a constant number always in the set_accepted_list_frozen before the other numbers are appended to the list set_accepted_list_frozen, how should i proceed?
set_accepted_list_frozen = set()
def constant_set(set_accepted_list,set_forbidden_list):
global set_accepted_list_frozen
if num_accepted >= len(set_accepted_list_frozen):
for var in set_accepted_list:
if len(set_accepted_list_frozen) == num_accepted:
break
set_accepted_list_frozen.add(var)
Related
I am new to python and my coding experience so far is with MATLAB.
I am trying to understand more about lists and dictionaries as i am using a library about DOEs that takes an dictionary as a passing argument.
But my trouble so far is that this dictionary assumes the form of ex.
DOE={'Elastic Modulus':[10,20,30], 'Density':[1,2,3], 'Thickness':[2,3,5]}
But i need this dictionary to be user defined, for example:
Have an input to define how many variables are needed (in this example are 3: Elastic Modulus','Density'and 'Thickness)
as the variables are defined, it should be able to store values in the dictionary over a for loop.
Is this possible using dictionaries?
Or is it better to use a list and convert in a dicionary later?
Thank you in advance
One can add keys and the corresponding values to a dict one at a time like so:
my_dict = {}
num_entries = int(input("How many entries "))
for _ in range(num_entries):
key = input("Enter the key: ")
value = input("Enter the value: ")
my_dict[key] = value
Presumably you would have a loop to do the entry of key and value for the number of values you wish to enter. Also if you are in python 2 it needs to be raw_input rather than input function. [Edit: Showing how to do the loop, since I noticed that was part of your question]
I'm trying to sample an item (which is one of the keys in a dictionary) from a list and later use the index of that item to find its corresponding value (in the same dictionary).
questions= list(capitals.keys())
answers= list(capitals.values())
for q in range(10):
queswrite = random.sample(questions,1)
number = questions.index(queswrite)
crtans = answers[number]
Here,capitals is the original dectionary from which the states(keys) and capitals(values) are being sampled.
But,apparently random.sample() method adds square brackets and single quotes to the sampled item and thus prevents it from being used to reference the list containing the corresponding values.
Traceback (most recent call last):
File "F:\test.py", line 30, in
number = questions.index(queswrite)
ValueError: ['Delaware'] is not in list
How can I prevent this?
random.sample() returns a list, containing the number of elements you requested. See the documentation:
Return a k length list of unique elements chosen from the population sequence or set. Used for random sampling without replacement.
If you wanted to pick just one element, you don't want a sample however, you wanted to choose just one. For that you'd use the random.choice() function instead:
question = random.choice(questions)
However, given that you are using a loop, you probably really wanted to get 10 unique questions. Don't use a loop over range(10), instead pick a sample of 10 random questions. That's exactly what random.sample() would do for you:
for question in random.sample(questions, 10):
# pick the answer for this question.
Next, putting both keys and values into two separate lists, then using the index of one to find the other is... inefficient and unnecessary; the keys you pick can be used directly to find the answers:
questions = list(capitals)
for question in random.sample(questions, 10):
crtans = capitals[question]
I have the following code which I have to build upon (i.e. it can't be written a different way). I know there are other better ways of achieving the end result, but I want to use this code and then repeat it to make a list.
from random import choice
number_list = range(1,1001) # Creates a list from 1 to 1000
random_from_list = choice(number_list) # Chooses a random number from the list
I want to now repeat the choice function above 100 times, then print that list of 100 random numbers that I have chosen from my list of 1000 numbers. I have read up on "for" loops but I can't see how to apply it here.
If you don't need to build up your list you could just print them one at a time:
for _ in range(100):
print(choice(number_list))
If you want to build your list first you can use a "list comprehension":
choices = [choice(number_list) for _ in range(100)]
print(choices)
for i in range(100):
print(choice(number_list))
I'm working on a Python assignment and I'm totally stuck. Any assistance would be greatly appreciated. I know it's probably not as convoluted as it seems in my head... The details are below. Thanks very much.
Implement the following three functions (you should use an appropriate looping construct to compute the averages):
allNumAvg(numList) : takes a list of numbers and returns the average of all the numbers in the list.
posNumAvg(numList) : takes a list of numbers and returns the average of all the numbers in the list that are greater than zero.
nonPosAvg(numList) : takes a list of numbers and returns the average of all the numbers in the list that are less than or equal to zero.
Write a program that asks the user to enter some numbers (positives, negatives and zeros). Your program should NOT ask the user to enter a fixed number of numbers. Also it should NOT ask for the number of numbers the user wants to enter. But rather it should ask the user to enter a few numbers and end with -9999 (a sentinel value). The user can enter the numbers in any order. Your program should NOT ask the user to enter the positive and the negative numbers separately.
Your program then should create a list with the numbers entered (make sure NOT to include the sentinel value (-9999) in this list) and output the list and a dictionary with the following Key-Value pairs (using the input list and the above functions):
Key = 'AvgPositive' : Value = the average of all the positive numbers
Key = 'AvgNonPos' : Value = the average of all the non-positive numbers
Key = 'AvgAllNum' : Value = the average of all the numbers
Sample run:
Enter a number (-9999 to end): 4
Enter a number (-9999 to end): -3
Enter a number (-9999 to end): -15
Enter a number (-9999 to end): 0
Enter a number (-9999 to end): 10
Enter a number (-9999 to end): 22
Enter a number (-9999 to end): -9999
The list of all numbers entered is:
[4, -3, -15, 0, 10, 22]
The dictionary with averages is:
{'AvgPositive': 12.0, 'AvgNonPos': -6.0, 'AvgAllNum': 3.0}
EDIT: This is what I have so far, which I did pretty quick just to have a something to work with but I can't figure out how to implement the keys/dictionary like the assignment asks. Thanks again for any help.
print("This program takes user-given numbers and calculates the average")
counter = 0
sum_of_numbers = 0
first_question = int(input('Please enter a number. (Enter -9999 to end):'))
while first_question != -9999 :
ent_num = int(input('Please enter a number. (Enter -9999 to end):'))
sum_of_numbers = sum_of_numbers + ent_num
counter = counter + 1
first_question = int(input('Please enter a number (Enter -9999 to end):'))
print("Your average is " + str(sum_of_numbers/counter))
Welcome to Python programming, and programming in general!
From your code, I assume you are not entirely familiar with Python lists, dictionaries, and functions and how to use them. I'd suggest you look up tutorials for these; knowing how to use them will make your assignment much easier.
Here are some tutorials I found with some quick searches that might help:
Dictionary Tutorial,
List Tutorial,
Function Tutorial
When your assignment says to make three functions, you should probably make actual functions rather than trying to fit the functionality into your loop. For example, here is a simple function that takes in a number and adds 5 to it, then returns it:
def addFive(number):
return number + 5
To use it in your code, you would have something like this:
num = 6 # num is now 6
num = addFive(num) # num is now 11
So what you should do is create a list object containing all the numbers the user entered, and then pass that object into three separate functions - posNumAvg, nonPosAvg, allNumAvg.
Creating a dictionary of key-value pairs is pretty easy - first create the dictionary, then fill it with the appropriate values. For example, here is how I would create a dictionary like {'Hello': 'World'}
values = {}
values['Hello'] = 'World'
print(values) # Will print out {'Hello': 'World'}
So all you need to do is for each of the three values you need, assign the result of the function call to the appropriate key.
If this doesn't feel like quite enough for you to figure out this assignment, read the tutorials again and play with lists, dictionarys, and functions to try and get a feel for them. Good luck!
P.S. The append method of lists will be helpful to you. Try to figure out how to use it!
I am using the following function to calculate the t-stat for data in data frame (x):
wilcox.test.all.genes<-function(x,s1,s2) {
x1<-x[s1]
x2<-x[s2]
x1<-as.numeric(x1)
x2<-as.numeric(x2)
wilcox.out<-wilcox.test(x1,x2,exact=F,alternative="two.sided",correct=T)
out<-as.numeric(wilcox.out$statistic)
return(out)
}
I need to write a for loop that will iterate a specific number of times. For each iteration, the columns need to be shuffled, the above function performed and the maximum t-stat value saved to a list.
I know that I can use the sample() function to shuffle the columns of the data frame, and the max() function to identify the maximum t-stat value, but I can't figure out how to put them together to achieve a workable code.
You are trying to generate empiric p-values, corrected for the multiple comparisons you are making because of the multiple columns in your data. First, let's simulate an example data set:
# Simulate data
n.row = 100
n.col = 10
set.seed(12345)
group = factor(sample(2, n.row, replace=T))
data = data.frame(matrix(rnorm(n.row*n.col), nrow=n.row))
Calculate the Wilcoxon test for each column, but we will replicate this many times while permuting the class membership of the observations. This gives us an empiric null distribution of this test statistic.
# Re-calculate columnwise test statisitics many times while permuting class labels
perms = replicate(500, apply(data[sample(nrow(data)), ], 2, function(x) wilcox.test(x[group==1], x[group==2], exact=F, alternative="two.sided", correct=T)$stat))
Calculate the null distribution of the maximum test statistic by collapsing across the multiple comparisons.
# For each permuted replication, calculate the max test statistic across the multiple comparisons
perms.max = apply(perms, 2, max)
By simply sorting the results, we can now determine the p=0.05 critical value.
# Identify critical value
crit = sort(perms.max)[round((1-0.05)*length(perms.max))]
We can also plot our distribution along with the critical value.
# Plot
dev.new(width=4, height=4)
hist(perms.max)
abline(v=crit, col='red')
Finally, comparing a real test statistic to this distribution will give you an empiric p-value, corrected for multiple comparisons by controlling the family-wise error to p<0.05. For example, let's pretend a real test stat was 1600. We could then calculate the p-value like:
> length(which(perms.max>1600))/length(perms.max)
[1] 0.074