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I get an error message that mentions a TypeError when I add
something to a list. What should I do?
If you get something like the following error.
TypeError: can only concatenate list (not "int") to list
you are likely trying to add an integer to a list.
Suppose you have two lists called x and y.
x = [0, 1, 2] y = [3, 4, 5]
And you would like to make a list that contains [0, 1, 2, 3].
You might try doing the following:
x + y[0]
Unfortunately, this is not allowed in Python, because addition
between a list and an integer is not defined. If you think about
it, this makes sense: how would you add a list to an integer?
Instead, recall that the + operator can be used to concatenate
two lists. Knowing this, we can put y[0] inside its own list
and concatenate that with the list x.
x + [y[0]]
Do our functions need to have the exact names that you have specified in the assignment? What about the variables for the inputs?
Your functions must have the exact names that we have
specified, or we won’t be able to test them. Note in particular
that the case of the letters matters, and that some of the
function names have one or more underscore characters (e.g.,
convert_to_inches).
For the variables specified for the inputs, you could in theory use different names, as long as they are still as descriptive as the original ones. However, when there are multiple inputs, you must keep the inputs in the same order that we specified in the assignment, or we won’t be able to test your function.
I’ve read about or used some Python functions that we have not discussed in lecture. Can I use them in the homework?
No. You should solve the problems in the homework using only constructs that we have discussed in lecture or that you have seen in the textbook. In addition, some of the problems have specific instructions regarding which functions you should or should not use. There are, of course, many different ways to accomplish the homework assignments, but we construct the assignments so that you can solve them using the tools that we have learned about in class.
As a reminder, you are prohibited from consulting with external sites such as Stack Overflow about the homework assignments, as well as from using ChatGPT or other generative AI tools when solving the homework problems. Please review our policies as needed.
Do we need to use recursion on this assignment?
No. None of the functions that we’re asking you to write for this assignment require recursion. If you wrote one or more of them using recursion, that’s okay, too, but doing so is not required.
I think I’m done with the assignment. Are there any things I should check before I submit?
I’m not sure exactly what I need to do when tracing functions. Do you have any suggestions?
We covered a similar tracing problem in lecture. That steps taken to solve that problem can also be seen in the pre-lecture video called Tracing Function Calls that can be found in the Blackboard folder for February 5’s lecture.
I’m having trouble figuring out how to write
the move_to_end() function. Do you have any hints?
We encourage you to start with some concrete cases. For example, we give you the following test case:
>>> move_to_end('computer', 3) result: 'putercom'
In this test case, the function needs to take the string
'computer' and create the string 'putercom'. In order to do
so, it needs to extract substrings of 'computer' and concatenate
them together.
s (which in this case is the string
'computer')? n (which in this case is 3)? By asking like these for this test case and other concrete cases, you should be able to come up with the general expression that you to construct the necessary return value. Also, don’t forget to handle the special case mentioned in the problem, which we recommend that you test for and handle first.
I’m having trouble figuring out how to write
the replace_end() function. Do you have any hints?
Here again, we encourage you to start with some concrete cases. For example, we give you the following test case:
>>> replace_start([1, 2, 3, 4, 5], [10, 11]) result: [1, 2, 3, 10, 11]
In this test case, the function needs to take the lists [1, 2, 3,
4, 5] and [10, 11] and create the list [1, 2, 3, 10, 11]. In
order to do so, it needs to extract a slice of the first list
and concatenate it to the second list.
values (which in this case is the list
[1, 2, 3, 4, 5])? new_start_vals (which in this case is [10, 11])? By asking questions like these for this test case and other concrete cases, you should be able to come up with the general logic that you can use to determine the necessary return value. Also, don’t forget to handle the special case mentioned in the problem, which we recommend that you test for and handle first.
I’m having trouble figuring out how to write
the repeat_elem() function. Do you have any hints?
Here again, try working through several concrete cases, following a similar procedure to the one we outlined above.
How can I repeat a string in Python?
In Python, you can repeat a string by using the * operator.
For example, if I wanted a string consisting of five a‘s, I could
do the following:
'a' * 5
Last updated on February 10, 2025.