OAU CSC 201 Practice Quiz

Tuples are represented with round brackets.

Loops over key, value pairs.

In most cases the value of two’s complement is different from the original value. However, there are cases in which the two’s complement value may be equal to the original value. For example, the two’s complement of 10000000 is also equal to 10000000. Hence the statement is false.

String formatting also allows conversion targets on the left to refer to the keys in a dictionary coded on the right and fetch the corresponding values. In the code shown above, (qty) and (food) in the format string on the left refers to keys in the dictionary literal on the right and fetch their assorted values. Hence the output of the code shown above is: 1 more spam.

The code shown above returns the address on the function ordi first, after which the word “Ordinary” is printed. Hence the output of this code is:
Address
Ordinary.

Since we have specified that the order of the output be: {a}, {0}, {abc}, hence the value of associated with {a} is printed first followed by that of {0} and {abc}. Hence the output of the code shown above is: ‘2.5, 10, [1, 2]’.

// is integer operation in python 3.0 and int(..) is a type cast operator.

The built in function vars() returns a dictionary containing all the variables that exist in the place. Hence the output of the code shown above is: {‘a’ : ‘hello’, ‘q’ : 10, ……..plus built-in names set by Python….}

If the truth method is not defined, the object is considered true. Hence the output of the code shown above is true.

The given number is -122. Here the total number of digits (including the negative sign) should be 6 according to the expression. In addition to this, there is a negative sign in the given print expression. Hence the output will be −−00122.

// is the operator for truncation division. It is called so because it returns only the integer part of the quotient, truncating the decimal part. For example: 20//3 = 6.

The expression shown above rounds off the given number to the number of decimal places specified. Since the expression given specifies rounding off to two decimal places, the output of this expression will be 56.24. Had the value been x=56.234 (last digit being any number less than 5), the output would have been 56.23.

The code ‘There are %d %s birds.’ %(4, blue) results in the output: There are 4 blue birds. When we insert more than one value, we should group the values on the right in a tuple.

Carefully look at the colons.

The code shown above is used to check whether a particular item is a part of a given set or not. Since ‘a’ is a part of the set z, the output is true. Note that this code would result in an error in the absence of the quotes.

SyntaxError, True is a keyword and it’s value cannot be changed.

The above expression returns the output 000345. It adds the required number of zeroes before the given number in order to make the number of digits 6 (as specified in this case).

0O11 is an octal number.

The symbol ‘&’ represents bitwise AND. This gives 1 if both the bits are equal to 1, else it gives 0. The binary form of 15 is 1111 and that of 12 is 1100. Hence on performing the bitwise AND operation, we get 1100, which is equal to 12.

To write single-line comments in Python use the Hash character (#) at the beginning of the line. It is also called number sign or pound sign. To write multi-line comments, close the text between triple quotes.
Example: “”” comment
text “””

Lists should be copied by executing [:] operation.

Error, objects of type int aren’t iterable.

i takes values 0, 1, 2 and 3.

The @ symbol along with the name of the decorator function can be placed above the definition of the function to be decorated works as an alternate way for decorating a function.

i takes values 0, 1, 2 and 3.

The expression not(10<20) returns false. The expression not(10>30) returns true. The and operation between false and true returns false. Hence the output is false.

The elements of the tuple are accessed by their indices.

The highest precedence is that of the exponentiation operator, that is of **.

In order to add ‘n’ blank spaces after a given string ‘S’, we use the formatting option:(“%-ns”%S).

Each object in Python has a unique id. The id() function returns the object’s id.

Coercion is the implicit (automatic) conversion of operands to a common type. Coercion is automatically performed on mixed-type expressions. The expression 1.7 % 2 is evaluated as 1.7 % 2.0 (that is, automatic conversion of int to float).

The same object is modified in the function.

Let’s break this down step by step so that it’s clear.

Code Analysis:

The Function:

def foo(x):

    x[0] = [‘def’]  # Changes the first element of the list `x` to [‘def’]

    x[1] = [‘abc’]  # Changes the second element of the list `x` to [‘abc’]

    return id(x)    # Returns the memory address (ID) of the modified list `x`

The Main Code:

q = [‘abc’, ‘def’]          # Creates a list `q` with two elements: [‘abc’, ‘def’]

print(id(q) == foo(q))      # Compares the memory address (ID) of `q` with the value returned by `foo(q)`

Step-by-Step Explanation:

1. List q Initialization:

• A list q is created:

q = [‘abc’, ‘def’]

• This list has an ID, which is its memory address. Let’s call it id(q).

2. Calling foo(q):

• The list q is passed into the function foo.

• Inside foo:

• x[0] = [‘def’]: The first element of the list is changed to [‘def’].

Now, q looks like this:

[[‘def’], ‘def’]

• x[1] = [‘abc’]: The second element of the list is changed to [‘abc’].

Now, q looks like this:

[[‘def’], [‘abc’]]

• The id(x) is returned. Since x and q refer to the same list, id(x) is the same as id(q).

3. Comparison (id(q) == foo(q)):

• The memory address of q is compared to the memory address returned by foo(q).

• Since foo(q) does not create a new list but modifies the same list, id(q) and id(x) are identical.

Output:

True

Key Points to Understand:

1. Lists are mutable: When you pass a list to a function, any changes made to the list inside the function will affect the original list because they share the same memory address.

2. The id() function: This returns the memory address of an object.

In the snippet of code shown above, three values are inserted into the target string. When we insert more than one value, we should group the values on the right in a tuple. The % formatting expression operator expects either a single item or a tuple of one or more items on its right side.

range(str) is not allowed.

Cause a decimal value of 0 to appear as output.

i is not in x[1:].

Within the subject string, curly braces represent substitution targets and arguments to be inserted. Hence the output of the code shown above:
‘hello, world, universe’.

The expression shown above results in the output 456.

OverflowError, cannot convert float infinity to integer.

math.pow() returns a floating point number.

The two codes shown above represent the same operation but in different formats. The output of both of these functions is: ‘0.33’. Hence the statement is true.