Python Concepts/Quizzes/Functions & classes

1 With the follow code

def parallel(x, y=1):
    return float(x * y) / (x + y)

parallel(2)

the follow happens:

	A syntax error as you cannot have assignments in the function argument
	An exception is raised as the second argument is missing when making a call to the function
	The result is approximately 0.6666 as the second argument is by default 1

2 With the two different definitions:

def first(n, m):
    "Bernoulli numbers computed as 1**m + 2**m + ... + n**m"
    return sum(map(lambda n: n**m, range(1,n+1)))

def second(n):
    # Bernoulli numbers computed as 1**m + 2**m + ... + n**m
    return sum(map(lambda n: n**m, range(1,n+1)))

True	False
		The first line in the body of the "second" function is a comment
		The first line in the body in the 'first' function will make a syntax error as you cannot have a string without an assignment inside a function.
		"first.__doc__" contains the string "Bernoulli numbers computed as 1**m + 2**m + ... + n**m"
		"second.__doc__" contains the string "Bernoulli numbers computed as 1**m + 2**m + ... + n**m"
		The first definition has a more standard Python documentation than the second definition

3 With the two above code

True	False
		help(first) will display the line "Bernoulli numbers computed as 1**m + 2**m + ... + n**m"
		dir(first) does not work as "first" is not a module

4 With the follow code

class Mammal():
    def number_of_legs(self):
        return 4

class Dog(Mammal):
    pass

class Human(Mammal):
    def number_of_legs(self):
        return 2

fido = Dog()
anna = Human()

we have:

True	False
		A class called "Mammal" is defined
		Mammal is a class derived from Dog
		Dog is a class derived from Mammal

5 With the above code we have:

True	False
		"anna" is an instance of "Human".
		fido.number_of_legs() makes an error.

6 We have that

__str__	__init__	__add__
			Is the name of the constructor method for a class
			Is the method associated with extending a list with another list

7 With the follow code

class Myint():
    def __init__(self, integer):
        self.integer = long(integer)
    def __add__(self, integer):
        return long(str(self.integer) + str(integer))

a = Myint(1)
b = a + 3
c = b + 4

we have

True	False
		b = 4
		b = 4L
		b = 13L
		c = 8
		c = 8L
		c = 17L
		c = 134L

8 We have

True	False
		True __add__ False will result in "True"
		In True or False the "or" is not the correct syntax

9 With the follow code

for n in range(10):
    if n == 2 or n == 6:
        continue
    elif n == 8:
        break
    print(n)
else: 
    print("Hello")

True	False
		The code will print 0 and 1 but finish after 2.
		You cannot have "else" there: The indentation in the block is wrong
		"Hello" will be printed several times

10 With the follow code

def bum():
    n = 1
    while True:
        if not n % 5 or 5 in map(int, list(str(n))):
            yield 'bum'
        else:
            yield n
        n += 1

bums = bum()
for b in bums:
   print(b)

True	False
		Clearly there is missing a 'return' statement somewhere
		Only integers from 1 to 5 are printed
		As the "while" loop is infinite then the "for" will at one point experience a memory problem when the number of elements gets too big.
		The if sentence examines whether 'n' is divisible with 5 or contains the decimal 5.