Python get the p-value of the array

Question

My task is that when the input is *X, every input is an array of one column with n rows, but they may have different rows(eg X[0] is an array with 1 column and 10 rows, and X[2] is with 1 column and 9 rows), I want the code counts the p-value of the every two arrays and get the lowest p-value and the order of X[n](eg. X[1] means the first array and so on). The code goes wrong, 'local variable ans_1 referred before assignment'. I don't know how to do with this.

def mass_independent_ttest(*X):
    min_pvalue = 10
    for i in range(0, len(X)):
        for j in range(i+1, len(X)):
            df_1 = pd.DataFrame(X[i])
            df_2 = pd.DataFrame(X[j])
            df_first = df_1.loc[:,0]
            df_second = df_2.loc[:,0]
            temp = scipy.stats.ttest_ind(df_first, df_second)
            temp_pvalue = temp.pvalue
            if temp_pvalue < min_pvalue:
                min_pvalue = temp_pvalue
                ans_1 = i
                ans_2 = j
    ans_tuple = (ans_1, ans_2, min_pvalue)
    return ans_tuple

`

Answer 1

At the last iteration of i , range(i+1, len(X)) will be an empty list, so that code won't execute, and ans_1 and ans_2 don't exist when you call ans_tuple = (ans_1, ans_2, min_pvalue) . So you should evaluate your outer and inner loops to see if you are getting the expected number of iterations.

This example shows conceptually what is happening.

for i in range(0, len(X)):
    print(list(range(i+1, len(X))))

=== Output: ===
[1, 2, 3, 4]
[2, 3, 4]
[3, 4]
[4]
[]