Question

Today, on the basis of answers I got here, I wrote this little code to create a random list of 16 elements.

import random

sources = ['Prone', 'Supine', 'Halfway', 'HalfInv']
result = [random.choice(sources)]
repeats = 0
fail = 0

while len(result) < 16:
    elem = random.choice(sources)
    repeats = result.count(elem)
    print(repeats)
    if (elem != result[-1]) & (repeats < 4):
        result.append(elem)
    else:
        fail = fail + 1
        print(fail)
        if fail > 100:
            result = [random.choice(sources)]

print(result)

Now what I’d like to do is:
1. to create 2 random lists naming them differently (how do I do this based on the for loop counter?)
2. put those 2 lists as columns in a tab delimited (txt) file, one next to the other in order to easily copy paste them in an excel file. I looked into csv module but it seems to only have methods for rows.

Answer 1

If you’re looking for a more efficient way to get a randomly ordered list of 4-of-each of your list elements from sources, try random.shuffle(list):

>>> import random
>>> random.seed()
>>> sources = ['Prone', 'Supine', 'Halfway', 'HalfInv']
>>> copy1 = sources * 4
>>> copy2 = sources * 4
>>> copy1 == copy2
True
>>> random.shuffle(copy1)
>>> random.shuffle(copy2)
>>> copy1 == copy2
False
>>> copy1
['HalfInv', 'Prone', 'Halfway', 'Supine', 'Prone', 'Halfway', 'Prone', 'Supine', 'Prone', 'HalfInv', 'HalfInv', 'Halfway', 'Supine', 'Halfway', 'HalfInv', 'Supine']
>>> copy2
['Prone', 'Halfway', 'Prone', 'Prone', 'HalfInv', 'Halfway', 'Halfway', 'HalfInv', 'Supine', 'HalfInv', 'Halfway', 'Supine', 'Prone', 'Supine', 'HalfInv', 'Supine']

Next, you wanted to generate and name the lists based on the loop counter… I’d recommend against this. Instead just append your random lists into a list one at a time, and you can index them in the order they were appended.

>>> n = 2 # number of random lists you want
>>> rand_lists = [] # A list for holding your randomly generated lists
>>> for i in range(n):
    sources_copy = sources * 4
    random.shuffle(sources_copy)
    rand_lists.append(sources_copy)

But this still leaves you with the problem that your data is in two separate lists. To remedy this you want the zip() function. It joins each element in list 1 with its correspondingly indexed element in list 2, forming a tuple at each index. This can be done with an arbitrary number of sequences.

>>> list1 = [1,2,3,4,5]
>>> list2 = ['a','b','c','d','e']
>>> zip(list1, list2)
[(1, 'a'), (2, 'b'), (3, 'c'), (4, 'd'), (5, 'e')]

To zip together your lists-within-a-list, use the * star unpacking operator before the name of your meta-list.

>>> my_data = zip(*rand_lists)

Now you want to output to a csv file; it’s easy enough to just write your own csv function. Remember that the column delimiters ate commas, the row delimiters are newlines.

def out_csv(mydata, filename):
    with open(filename, 'w') as out_handle:
        for line in mydata:
            out_handle.write(','.join(line) + '\n')

From here just pass your zipped list combo into the out_csv function, and make sure your filename has the .csv extension. Excel can natively read in .csv files so you shouldn’t need to do any copy-pasting.

Here’s the last step:

>>> out_csv(my_data, 'my_name.csv')