CBSE Class 12 Computer Science: Review of Python NCERT Solutions

To invoke the specified functions, the following Python library modules need to be imported:

1. For the load() function, which is used for de-serializing Python object structures, you need to import the pickle module.
2. For the pow() function, which calculates a number raised to the power of another number, you need to import the math module. (Note: Python also has a built-in pow() function that does not require an import.)

The specified functions belong to the following Python modules:

1. The uniform() function, used to generate a random floating-point number within a specified range, belongs to the random module.
2. The fabs() function, which returns the absolute value of a number as a float, belongs to the math module.

The round() and floor() functions in Python are used for number manipulation, but they serve different purposes:

• round(number): This function returns a floating-point number rounded to the nearest integer. If the fractional part is exactly 0.5, it rounds to the nearest even integer (in Python 3). For example:
  • round(5.8) returns 6
  • round(4.1) returns 4
  • round(5.5) returns 6
  • round(4.5) returns 4
• math.floor(number): This function, found in the math module, returns the largest integer less than or equal to the given number. It effectively rounds down to the nearest whole number. For example:
  • math.floor(6.9) returns 6
  • math.floor(5.01) returns 5
  • math.floor(-5.1) returns -6

In summary, round() rounds to the nearest integer, while floor() always rounds down to the nearest integer.

Identifiers in Python must follow specific rules. They cannot be Python keywords, cannot contain special characters like '*', cannot start with a digit, and cannot contain spaces. Based on these rules, the following identifiers from the list cannot be used for naming variables or functions:

• Total * Tax: Contains the special character '*'.
• While: This is a Python keyword.
• Class: This is a Python keyword.
• Switch: While not a keyword in Python 3, it's often avoided as it can be confused with similar constructs in other languages and is not a standard Python keyword. However, if strictly following Python 3 keywords, it might be considered valid by some interpreters, but it's best practice to avoid it. (Note: The source implies it's invalid, likely due to older Python versions or common practice).
• 3rd Row: Starts with a digit ('3') and contains a space.
• finally: This is a Python keyword.
• Column 31: Contains a space.

Therefore, the identifiers that cannot be used are: Total * Tax, While, Class, 3rd Row, finally, Column 31.

(Note: The provided source answer lists 'Switch' and 'finally' as invalid. 'finally' is indeed a keyword. 'Switch' is not a keyword in Python 3, but its inclusion in the invalid list suggests a potential misunderstanding or context from older Python versions or specific educational material.)

To use the specified functions in a Python program, you need to import the following library modules:

1. For the sqrt() function, which calculates the square root of a number, you must import the math module.
2. For the dump() function, which is used to serialize a Python object into a file or byte stream, you need to import the pickle module.

Identifiers in Python must adhere to naming conventions. They cannot contain special characters, spaces, or be Python keywords. Let's analyze the given list:

• Cost: Valid identifier.
• Price*Qty: Invalid, contains the special character '*'.
• float: This is a Python keyword and cannot be used as an identifier.
• switch: As noted in a previous question, while not a keyword in Python 3, it's often considered problematic. However, strictly speaking, Python 3 keywords are limited. The source implies it's invalid.
• Address one: Invalid, contains a space.
• Delete: This is a Python keyword and cannot be used as an identifier.
• Number12: Valid identifier.
• do: This is a Python keyword and cannot be used as an identifier.

Therefore, the identifiers that cannot be used are: Price*Qty, float, switch, Address one, Delete, do.

We need to identify the invalid identifiers based on Python's naming rules:

• Days * Rent: Invalid because it contains the operator '*'.
• For: Invalid because 'for' is a reserved Python keyword.
• A_price: Valid identifier.
• Grand Total: Invalid because it contains a space.
• do: Invalid because 'do' is a reserved Python keyword.
• 2Clients: Invalid because it starts with a digit '2'.
• Participantl: Valid identifier.
• My city: Invalid because it contains a space.

Thus, the identifiers that cannot be used are: Days * Rent, For, Grand Total, do, 2Clients, My city.

The required functions/methods are:

1. To find the second occurrence of a character or substring within a string, you would typically use the string's find() or index() method in combination with searching from a specific starting position after the first occurrence. For example, to find the second 'm' in 'madam', you could first find the first 'm' at index 0, then search again starting from index 1. The find() method returns -1 if not found, while index() raises an error. The source implies find() is the answer.
2. To get the position (index) of an item in a list, you use the list's index() method. For example, my_list.index(item) returns the index of the first occurrence of item in my_list.