Look up the “fizz buzz” problem, that’s an excellent example of if/elif/else

Hey there! Some very good questions there. Celsius > Fahrenheit question Bracket notation, like [-1] can be used for more than just lists. In this example, it's grabbing the last character of the temp string, which is expected to be F or C Reverse word question This comes down to the fact that indexes start at 0. Let's say we use the word "chicken". len(word) would be 7, and so len(word)-1 would be 6. This range would start at 6 The next -1 is the stopping point. Because range() excludes the given value, so 0 is included in the range The final -1 is the step, so this returns the range of 6 down to 0 (inclusive) counting backward So the final range of numbers produced is 6, 5, 4, 3, 2, 1, 0, which targets all 7 letters of "chicken" Two-dimensional array question This is a Python List comprehension. There is a new Workshop that is about to be released that goes into depth about this. In the meantime, this Workshop gives an overview of how List Comprehensions work (https://teamtreehouse.com/library/python-comprehensions) - for col in range(col_num): This is a loop that iterates over the range of values from 0 to col_num - 1. The variable col takes on each value in this range one at a time. - 0 for col in range(col_num): This expression assigns the value 0 to each iteration of the col variable. In other words, it creates a list containing col_num number of 0s. - for row in range(row_num): This is another loop that iterates over the range of values from 0 to row_num - 1. The variable row takes on each value in this range one at a time. - [0 for col in range(col_num)]: This list comprehension creates a list of col_num number of 0s. It's essentially the same expression as step 2. - [[0 for col in range(col_num)] for row in range(row_num)]: This is a nested list comprehension where the outer loop iterates over the range of values from 0 to row_num - 1, and for each iteration, the inner loop creates a list of col_num number of 0s. The result is a 2-dimensional list (a list of lists) with row_num rows and col_num columns, where each element is 0. In summary, the line of code creates a 2D list filled with zeros, with dimensions specified by row_num and col_num. Binary Numbers Question This is also a Python List Comprehension. Be sure to refer to the Workshop mentioned above (and watch out for the new one that's coming out soon!). This line produces a list of values. The input() is split into a list by the , delimiter. Each of these (ie, 0100, 0011, etc) is appended to the new num list The % operator is the modulo. Read more about the modulo here (https://www.mathsisfun.com/numbers/modulo.html). x%5 will result in an integer. Positive numbers are treated as True, while 0 is treated as False. Since something that is divisible by 5 will return 0, this conditional will return True if x is divisible by 5, because not 0 (False) evaluates to True 'D' pattern question for column in range(0, 7): This is a loop that iterates over the range of values from 0 to 6 (inclusive) using the variable column. if (column == 1 or ((row == 0 or row == 6) and (column > 1 and column < 5)) or (column == 5 and row != 0 and row != 6)): This condition determines whether the code inside the if statement block should be executed. It combines three different conditions using logical operators (or and and): column == 1: This checks if the value of column is equal to 1. The first part, (row == 0 or row == 6), checks if the value of row is equal to 0 or 6. (column == 5 and row != 0 and row != 6): This condition checks if the value of column is equal to 5 and if the value of row is not equal to 0 and not equal to 6. If any of these conditions evaluate to true, the code inside the if statement block will be executed. print("*"): This line prints an asterisk character (*). If the conditions in the if statement are true, the code inside the if statement block will be executed, and an asterisk will be printed. To summarize, this code snippet iterates over the range of values from 0 to 6 using column, and for each value of column, it checks the conditions specified in the if statement. If any of the conditions are true, it prints an asterisk.