# Example exam problems for Part A (Pitfalls)
# Tip: Try to add 4-5 of your own syntax, semantic, style errors
# in code you've done on assignments (refer to grading feedback for ideas!)
# Reminder: For full credit, you must clearly identify the distinct
# errors and justify why they are an error/issue.

# Pitfalls 1: Syntax Errors
# The following code has 5 distinct Python _syntax_ errors.
# What are they?

from math import sqrt

def is_prime(n):
    ""
    Return True if 'n' is prime; else return False.
    ""
     if n == 2 or == 3:
         return True
     elif n % 2 = 0:
         return False
     else
         for i in range(5, int(sqrt(n) + 1), 2):  # odd #s >= 5
             if n % i == 0:
                 return False
         return True

# Syntax errors:
- 1. On Line 17, n % 2 = 0 should be n % 2 == 0 because
     = is the operator for assignment, but elif syntax expects
     a boolean evaluation (n % 2 == 0 evaluates to a boolean)
- 2.
- 3.
- 4.
- 5.

# Pitfalls 2: Semantic Errors
# The following code has 5 distinct _semantic_ (behavior) errors.
# What are they?

def factorial(n):
    """
    Compute and return the factorial of n i.e.
    n * (n - 1) * (n - 2) * ... * 1, or 1 if n == 0.
    """
    assert n >= 0
    while True:
        n -= 1
        if n <= 0:
            return
        result = n * result
    print(result)

def e(limit):
    """
    Estimate the constant e (2.71828...) by the series expansion:

      e = sum (i from 0 to infinity) (1 / factorial(i)),

    except we use a limit to cut off the expansion
    (OK if the limit is large enough).
    """
    result = 0
    for i in range(0, limit + 1):  # 0 to limit, inclusive
        result += 1 / factorial(i)
    return result

print(e(20))  # should print 2.7182818284590455

# Pitfalls 2: Semantic Errors
- 1.
- 2.
- 3.
- 4.
- 5.

# Pitfalls 3: Style Errors
# The following code has 5 distinct _style_ errors.
# What are they?
def w(x, y, z):
    "rt es in x in [y-z,y+z]."
    v=[]
    for i in x:
     if i >= y - z and i <= y + z:
               v+=[i]
     else:
         i=i
    return v

# Style Errors
- 1.
- 2.
- 3.
- 4.
- 5.
- 6.


# Another example exercise for style (from 23fa Lecture 26 demo)
 1 def count_shared(dict1, dict2):
 2   """
 3   Returns the number of key/value pairs in dict1 that are
 4   also in dict2. e.g. {'a': 'x', 'b': 'y', 'c': 'x', 'e': 'x'} shares
 5   2 key/value pairs with {'a': 'x', 'b':'x', 'c':'x', 'd':'x'}
 6   ('a':'x' and 'c':'x').
 7   """
 8   count = 0
 9   keys = list(dict1.keys())
10   for i in range(len(keys)):
11       key = keys[i]
12       for key2 in dict2:
13           if keys[i] == key2:
14               a = dict1[key]
15               b = dict2[key2]
16               if a == b:
17                   count += 1
18   return count


# Style Errors
- 1. Various variable names are undescriptive, such as a, b, key, key2
     This is a style issue because it detracts from readability (for others
     or the author reading it later) and can lead subtle bugs.
- 2.
- 3.
- 4.
- 5.
- 6.

# Example of a solution a student may provide to support their answer
# (we came up with this at the end of class); we won't deduct on minor issues
# since you aren't allowed to use any debugger/tools or run the program,
# and it can help justify your written answers more clearly (e.g. this problem
# in particular has a lot of logical redundancy that can be cleaned up in
# multiple lines)
Improved code:
 1 def count_shared(dict1, dict2):
 2   """
 3   Returns the number of key/value pairs in dict1 that are
 4   also in dict2. e.g. {'a': 'x', 'b': 'y', 'c': 'x', 'e': 'x'} shares
 5   2 key/value pairs with {'a': 'x', 'b':'x', 'c':'x', 'd':'x'}
 6   ('a':'x' and 'c':'x').
 7   """
 8   count = 0
     # Loop through dict1's keys to see if the key is also in dict2
     for key in dict1:  # same as list(dict1.keys())
        if key in dict2:
            val1 = dict1[key]
            val2 = dict2[key]
            if val1 == val2:
                count += 1
    return count