PCAP Flashcards — Free Certified Associate Python Programmer PCAP Study Cards

if __name__ == '__main__': run() / if __name__ == '__main__': run()

Both options A and B are correct because they are identical and represent the standard Python idiom `if __name__ == '__main__': run()`. When the script is run directly, Python sets `__name__` to `'__main__'`, triggering the function. When imported, `__name__` is the module name, so the function is not executed. Options C and D are incorrect: C relies on an environment variable that is not standard, and D checks `sys.argv[0]` which is the script path, not the module name.

print(mypackage.__file__)

`mypackage.__file__` returns the filesystem path from which the module was loaded, allowing the developer to see exactly which `mypackage` Python is using. This directly reveals if the wrong package (e.g., from a different location or a conflicting installation) is being imported instead of the intended one.

'This is a test. Is this a test?'.count('is')

Python's string method `count(substring)` returns the number of non-overlapping occurrences of the substring in the string. In 'This is a test. Is this a test?', 'is' appears twice (in 'This' and 'is'), and the method counts them correctly, ignoring case sensitivity (the capitalized 'Is' is not counted).

Use re.search(r'\bexcellent\b', review, re.IGNORECASE)

`re.search(r'\bexcellent\b', review, re.IGNORECASE)` uses the `\b` word boundary anchor to ensure that 'excellent' is matched as a whole word, not as part of another word like 'unexcellent'. The `re.IGNORECASE` flag handles case-insensitive matching, covering 'Excellent', 'EXCELLENT', etc. This approach also correctly handles punctuation attached to the word, such as 'excellent!', because the word boundary matches between a word character and a non-word character.

str.split()

Str.split(), is the most appropriate because it splits a string on whitespace by default. Although the timestamp 'YYYY-MM-DD HH:MM:SS' contains a space, using split() without arguments returns a list of all space-separated elements. Since the timestamp is always the first two elements (date and time), the developer can join them with a space to get the full timestamp. Alternatively, split() can be used with a specified separator and maxsplit to achieve the desired split. This flexibility makes str.split() the best choice among the given options.

Raise NotImplementedError inside the method body

Raising NotImplementedError inside the base class method is the standard Python idiom for defining an abstract-like method that must be overridden in subclasses. If a subclass fails to override the method and it is called, Python will raise an explicit error at runtime, preventing accidental use of the base implementation. This approach enforces the contract that the method is intended only for subclasses, without requiring the `abc` module.

Method overriding

Method overriding is the mechanism where a subclass provides a specific implementation of a method that is already defined in its superclass. In this scenario, SavingsAccount overrides the withdraw method from BankAccount to add penalty logic, which is the defining characteristic of method overriding in Python.

The file handle is opened in the __init__ method of the base class

If the file handle is opened in the `__init__` method of the base class, each time a new instance is created (including when an `AppLogger` instance is created), a new file handle is opened. This means the `Logger` class and the `AppLogger` class do not share the same file handle; instead, each instance gets its own handle. To share a single file handle across all instances, the file handle should be opened as a class attribute or in a class method, not in `__init__`.

Liskov Substitution Principle

The Liskov Substitution Principle (LSP) states that objects of a superclass should be replaceable with objects of its subclasses without affecting the correctness of the program. In this scenario, 'calculate_area(shape)' accepts a 'Shape' instance, and because both 'Circle' and 'Square' are proper subtypes that honor the contract of the 'area' method, the function works correctly regardless of which subclass is passed. This is the core of LSP: substitutability without side effects.

__getitem__ and __len__

To make a class behave like a sequence and support indexing (e.g., obj[0]), Python requires the __getitem__ method to retrieve items by key. Additionally, the __len__ method is needed to define the length of the sequence, which is used by built-in functions like len() and is part of the sequence protocol. Together, these two methods satisfy the minimal requirements for a sequence-like object that supports indexing.

2 2 2

The code defines a class `A` with a class variable `x = 2`, and a class `B` that inherits from `A`. The `display` method prints `self.x`, which first looks up the instance attribute `x`; since no instance attribute is set, it falls back to the class variable `x = 2` from class `A`. The loop creates three instances of `B` and calls `display` on each, so each prints `2` on a separate line, resulting in the output 2, 2, 2.

Override __init__ to accept a message and call super().__init__(message).

The `Exception` class's `__init__` method stores the message argument in the `args` attribute, which is used by the default `__str__` method to display the message. By overriding `__init__` to accept a message and call `super().__init__(message)`, the custom exception properly passes the message to the base class, ensuring it is displayed when caught and printed.

It always executes, regardless of exceptions.

The `finally` block in Python is designed to always execute after the `try` and `except` blocks, regardless of whether an exception was raised or not. This includes cases where a `return`, `break`, or `continue` statement is executed in the `try` block, or even if an unhandled exception occurs. The `finally` block is guaranteed to run before the function returns or the exception propagates, ensuring cleanup actions like closing files or releasing resources.

8080

The code reads the config.txt file and splits its content by newlines. The first line contains 'port=8080', and after splitting by '=', the second element is '8080'. The int() function converts this string to the integer 8080, which is then printed. Option C is correct because the output is the integer 8080, not a string or quoted form.

FileNotFoundError

`FileNotFoundError` is a specific subclass of `OSError` that is raised exactly when a file or directory is requested but does not exist. By catching only `FileNotFoundError`, the function handles the missing-file scenario without masking other I/O errors such as permission issues or disk failures, which is the precise requirement stated in the question.

Catch the exception, log the full traceback, then raise a custom generic exception.

It balances security and debugging: the full traceback is logged for developers (preserving debugging details like file paths), while a custom generic exception is raised to end users, preventing sensitive information from being exposed. This approach follows the principle of least privilege for error handling, ensuring that internal details are not leaked to untrusted sources.

Wrap the log write in a try/except that catches OSError and writes to stderr as fallback.

It uses a targeted try/except block around only the log write operation, catching OSError (which includes disk-full conditions) and falling back to stderr. This prevents the main application from crashing while still reporting the error, adhering to the principle of handling exceptions at the point where they occur and only when you can meaningfully recover.