OAU CSC 201 Practice Quiz

// 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.

Expression 1 is evaluated as: 2**9, which is equal to 512. Expression 2 is evaluated as 8**2, which is equal to 64. The last expression is evaluated as 2**(3**2). This is because the associativity of ** operator is from right to left. Hence the result of the third expression is 512.

eval can be used as a variable.

Pickling is the process of serializing a Python object, that is, conversion of a Python object hierarchy into a byte stream. The reverse of this process is known as unpickling.

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

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

The code shown above shows the formatting option on the same value, that is 4.56, where in the second case, the value is enclosed in a list. Hence the output of the code shown above is:
‘4.56’, ‘[4.56]’

Error, objects of type float cannot be interpreted as an integer.

The function not returns true if the argument amounts to false, and false if the argument amounts to true. Hence the first function returns false, and the second function returns false.

The code shown above shows a general decorator which can work with any number of arguments.

String x is not being altered and i is in x[:-1].

The result of the expression shown will be 1011. This is because we have not specified the base in this expression. Hence it automatically takes the base as 10.

Neither of 0.1, 0.2 and 0.3 can be represented accurately in binary. The round off errors from 0.1 and 0.2 accumulate and hence there is a difference of 5.5511e-17 between (0.1 + 0.2) and 0.3.

Understanding Arithmetic Operators with Strings:

1. * (Multiplication):
• Strings can be multiplied with integers to create repeated copies of the string.
• Example:

print(“abc” * 3) # Output: abcabcabc

• Allowed with strings.

2. – (Subtraction):
• Subtraction is not defined for strings in Python. You cannot subtract one string from another.
• Example:

print(“abc” – “a”) # This will raise a TypeError.

• Not allowed with strings.

3. + (Addition):
• Strings can be concatenated (joined) using the + operator.
• Example:

print(“abc” + “def”) # Output: abcdef

• Allowed with strings.

4. All of the mentioned:
• Since both * and + are allowed with strings, not all arithmetic operators are disallowed. Only – (subtraction) cannot be used with strings.

Correct Answer:

b) –

Subtraction (-) is the arithmetic operator that cannot be used with strings in Python.

The expression int(1011,2) results in an error. Had we written this expression as int(‘1011’,2), then there would not be an error.

The code shown above demonstrates rebinding using a static method. This can be done with or without a decorator. The output of this code will be 100.

When the value of x is equal to 8 (1000), then x>>2 (bitwise right shift) yields the value 0010, which is equal to 2. Hence the value of x is 8.

range(int(2.0)) is the same as range(2).

Although the presence of parenthesis does affect the order of precedence, in the case shown above, it is not making a difference. The result of both of these expressions is 1.333333333. Hence the statement is true.

The ^ operator represent bitwise XOR operation. &: bitwise AND, | : bitwise OR and ! represents bitwise NOT.

Execute help(id) to find out details in python shell.id returns a integer value that is unique.Execute help(id) to find out details in python shell.id returns a integer value that is unique.

Functions are reusable pieces of programs. They allow you to give a name to a block of statements, allowing you to run that block using the specified name anywhere in your program and any number of times.

Execute help(math.trunc) to get details.

The value of the expression (2**2)**3 = 4**3 = 64. When the expression 2**2**3 is evaluated in python, we get the result as 256, because this expression is evaluated as 2**(2**3). This is because the associativity of exponentiation operator (**) is from right to left and not from left to right.

Python first searches for the local, then the global and finally the built-in namespace.

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

Variable x is incremented and printed twice.

range(str) is not allowed.

The expression shown above does not result in an error. The output of this expression is -%5d0 989. Hence this statement is incorrect.

The code shown above first prints the word “Decorated” and then “ordinary”. Hence the output of this code is:
Decorated
Ordinary.

The expression shown above results in the output 456.

This is a built-in function which rounds a number to give precision in decimal digits. In the above case, since the number of decimal places has not been specified, the decimal number is rounded off to a whole number. Hence the output will be 5.

The result of the expression shown above is 1.0 because print rounds off digits.

[::-1] reverses the list.

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.

Built-in functions and user defined ones. The built-in functions are part of the Python language. Examples are: dir(), len() or abs(). The user defined functions are functions created with the def keyword.

All the statements will execute successfully but at the cost of reduced readability.

Python shell throws a NoneType object back.

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).

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’.

l (or L) stands for long.

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.

The code shown above returns a new list containing only those elements of the list l which do not amount to zero. Hence the output is: [1, 2, ‘hello’].

List data type can store any values within it.

The else part is not executed if control breaks out of the loop.

pip is a package manager for python. Which is also called Preferred Installer Program.

The above expression is an example of explicit conversion. It is evaluated as: float(4+int(2.39)%2) = float(4+2%2) = float(4+0) = 4.0. Hence the result of this expression is 4.0.

Loops over key, value pairs.