1. ­­­Python Versus C++: An Analysis of Student Struggle on Small Coding Exercises in Introductory Programming Courses
Nabeel Alzahrani1, Frank Vahid1,3, Alex Edgcomb1,3, Kevin Nguyen1 and Roman Lysecky2,3  

1 Computer Science and Engineering, University of California, Riverside 

2 Electrical and Computer Engineering, University of Arizona

3 zyBooks, Los Gatos, California  

Frank Vahid, UC Riverside, 2018

2. Frank Vahid, UC Riverside, 2018
CS 1
Before
After
C++ for majors + non-majors
CS1 at 67 univ.
Considering Python option for non-majors
Easier to learn / less struggle?
Demand
Frank Vahid, UC Riverside, 2018

3. Similar C++ and Python zyBooks, widely-used
Frank Vahid, UC Riverside, 2018

4. Frank Vahid, UC Riverside, 2018
Python
Frank Vahid, UC Riverside, 2018

5. Coding challenge activities (CAs) -- Homework
Frank Vahid, UC Riverside, 2018

6. Coding Challenge Activities -- CA (Homework)
Frank Vahid, UC Riverside, 2018

7. Frank Vahid, UC Riverside, 2018

8. Raw anonymized submissions for each CA
Time of submission
User #
Answer correct
Submitted solution
3/10/2017
1:20:44 PM
0255 No
while (userNum != 1){
     cout << userNum << " ";
     userNum = userNum / 2;
     }
...
3/10/2017  
1:24:51 PM
while (userNum !=0){
     while (userNum != 1){
        cout << userNum << " ";
        userNum = userNum / 2;
        }
  cout << userNum << " ";
1:30:18 PM
Yes
while (userNum >= 1){
Frank Vahid, UC Riverside, 2018

9. Considered 11 ~identical CAs in C++ & Python
CA title
Ch #
Chapter Title 1
Tree Height 2
Vars / Assgnmt
Basic while loop expression 4
Loops 3
Simon says
Vector iteration: Sum excess 5
Arrays / Vectors
Function call in expression 6
User-Def Fcts
Function errors: Copying one function to create another 7
Function with loop: Shampoo. 8
Constructor overloading
Objs & Classes 9
Basic inheritance 10
Inheritance
Derived class membr override 11
Recursive function: Writing the base case 12
Recursion
Frank Vahid, UC Riverside, 2018

10. Obtained anonymized submissions for 21 similar schools
School pair
Total # students in C++
Total # students in Python
1 (Research universities)
153
105
2 (Community colleges) 13 33
3 (Teaching universities) 34 23
4 (Research universities)
277
176
5 (Same community college) 21 29
6 (Teaching universities) 48 35
7 (Research universities)
121 92
8 (Community colleges) 14
165
9 (Community colleges) 15 17
10 (Research universities)
167
195
11 (Teaching universities)
194
N/A
Total number of students
1057
870
Frank Vahid, UC Riverside, 2018

11. Analyzed submissions for “struggle rate”
Struggling student =
((time > 5 min.) AND (# attempts > 3)
AND (time > (2 * Baseline time)) AND (# attempts > (2 * Baseline attempts)))
OR (time > 15 min.)
Struggle rate = # struggling students / # students
In other words: Excessive time or # of submissions
Frank Vahid, UC Riverside, 2018

12. RESULTS: C++ vs. Python struggle rate (21 schools, 1,927 students)
Frank Vahid, UC Riverside, 2018

13. No computing prerequisites
Majors
Non-Majors
Frank Vahid, UC Riverside, 2018

14. Manually examined mistakes causing struggle
Simple geometry can compute the height of an object from the object's shadow length and shadow angle using the formula: tan(angleElevation) = treeHeight / shadowLength.  1. Using simple algebra, rearrange that equation to solve for treeHeight.  2. Write a statement to assign treeHeight with the height calculated from an expression using angleElevation and shadowLength.  CA
C++
Python 1
Struggle % = 5
treeHeight = tan(angleElevation) * shadowLength;
Not knowing how to convert a math equation
Using / instead of *
Missing tan() for the angleElevation variable
Mistyping variable names
Struggle % = 9
tree_height = math.tan(angle_elev) * shadow_len
Using tan() instead of math.tan()
Wrong assignment (using two = symbols,
assign to the wrong variable, reverse assignment, etc.)
Frank Vahid, UC Riverside, 2018

15. Frank Vahid, UC Riverside, 2018CA
C++
Python 7
Struggle % = 27
void PrintShampooInstructions( int numCycles) {
  if (numCycles < 1) {
     cout << "Too few." << endl;
  }
  else if (numCycles > 4) {
     cout << "Too many." << endl;
  else {
     for (int N = 1; N <= numCycles; N++){
      cout << N << ": Lather and rinse." << endl;
     }
     cout << "Done." << endl; }
Missing for-loop
Missing for-loop counter inside for-loop
Wrong for-loop counter initial value
Wrong for-loop condition
Wrong for-loop location
Wrong cout() argument inside for-loop
Struggle % = 44
def shampoo_instructions(num_cycles):    if num_cycles < 1:
       print('Too few.')
   elif num_cycles > 4:
       print('Too many.')
   else:
       for N in range(1,num_cycles+1):
           print(N, ': Lather and rinse.')
       print('Done.')
Wrong while-loop update (when using while-loop)
Wrong print() argument inside for-loop
Missing with for-loop condition variable inside for-loop
Frank Vahid, UC Riverside, 2018

16. Results from manual examination
Basic logic errors cause most struggle
Similar errors in C++ and Python
Just more common by Python students
Frank Vahid, UC Riverside, 2018

17. Frank Vahid, UC Riverside, 2018
Conclusions
Analyzed struggle for 11 same Python & C++ zyBook short coding activities across ~20 schools (~1,000 students each, at similar schools)
Python struggle rate not lower; actually ~2x higher
Most mistakes due to logic errors
But…
Other reasons for switching to Python
Just one of many possible analyses
Student/teacher populations might differ
May help CS 1 teachers decide if should switch, or influence how taught
Frank Vahid, UC Riverside, 2018