PCPP1 Practice Test 20 — 15 Questions

Question 1

You are prototyping a Tkinter application and want a single-line input field where users can type a search term. The field should also show a placeholder-like behavior by pre-filling the text 'Search...' when the window opens. Which widget and option combination achieves this most directly?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

An Entry widget with a StringVar whose initial value is 'Search...' and passed via the `textvariable` option.. An Entry widget is the canonical single-line text input in Tkinter. Pairing it with a StringVar initialized to the placeholder text and connected via `textvariable` gives both an initial visible value and a live binding that the application can read or update. This directly satisfies the requirement of a pre-filled, editable search field without extra workarounds.

Answer

A Text widget with `height=1` and the initial string passed as the first positional argument.

Answer

A Spinbox widget with `values=('Search...',)` and `state='readonly'` so the placeholder cannot be modified.

Answer

A Label widget with `textvariable` bound to a StringVar set to 'Search...' and made editable via `state=tk.NORMAL`.

Question 2

You are writing a Python script that must process a large text file line by line. The file is UTF-8 encoded, but some lines contain characters that are not representable in the default system encoding. You want to ensure that the script reads the file correctly on any platform. Which code correctly opens the file?

Accepted Answer

open('data.txt', 'r', encoding='utf-8'). Specifying `encoding='utf-8'` when opening a text file ensures consistent decoding across platforms. Relying on the default encoding can cause errors on systems where the default is not UTF-8. The `errors` parameter should not be used to mask decoding issues when the goal is correct reading.

Answer

open('data.txt', 'r')

Answer

open('data.txt', 'r', errors='ignore')

Answer

open('data.txt', 'rb')

Question 3

How do you define a property in a class to make it read-only?

Accepted Answer

Define a property with only @property, no @setter.. By defining the property with only a getter (using @property) and omitting the setter method.

Answer

Use the 'readonly' decorator.

Answer

Use the 'final' modifier.

Answer

Set the attribute to private.

Question 4

Which TWO of the following are valid ways to define a configuration option in configparser?

Accepted Answer

parser['section']['option'] = 'value'. Option A is correct because configparser supports the mapping-style interface, so assigning parser['section']['option'] = 'value' creates or updates the option 'option' in 'section' with the string 'value'. Option D is correct because the ConfigParser.set(section, option, value) method is the explicit API for setting an option's value within a section, and it requires the section to already exist. Options B, C, and E are not valid configparser methods: add_option, write, and insert do not exist with those signatures — write() actually writes the configuration to a file-like object, and there is no add_option or insert method for defining options.

Answer

parser.add_option('section', 'option', 'value')

Answer

parser.write('section', 'option', 'value')

Answer

parser.insert('section', 'option', 'value')

Question 5

A developer is writing a Python script and wants to ensure that the code adheres to PEP 8's recommendations for blank lines. According to PEP 8, how many blank lines should surround a top-level function definition?

Accepted Answer

Two blank lines before and after the function definition.. PEP 8 recommends two blank lines before and after top-level function and class definitions. This provides clear visual separation and improves readability. One blank line is used for methods inside classes, and no blank lines would make the code cramped. Three blank lines are excessive. The correct choice is two blank lines.

Answer

No blank lines are required; the function can be adjacent to other code.

Answer

One blank line before and after the function definition.

Answer

Three blank lines before and after the function definition.

Question 6

Which THREE of the following are correct regarding socket buffer sizes?

Accepted Answer

Buffer sizes are limited by the operating system. Option A is correct because socket buffer sizes are bounded by OS-level limits such as net.core.rmem_max and net.core.wmem_max on Linux, so an application cannot arbitrarily set them beyond what the kernel permits. Option B is correct because the SO_RCVBUF socket option specifically controls the size of the receive buffer used to hold incoming data before the application reads it. Option E is correct because setsockopt() is the standard API call used to configure socket options like SO_RCVBUF and SO_SNDBUF on a socket. Option C is wrong because buffer size directly influences throughput, especially on high-bandwidth or high-latency links where too small a buffer limits the window. Option D is wrong because excessively large buffers can waste memory, increase latency, and do not guarantee faster transfer since throughput is also constrained by bandwidth, RTT, and application processing.

Answer

The buffer size has no effect on throughput

Answer

Setting a massive buffer always improves speed

Question 7

You are building a Python script that consumes a REST API which returns paginated JSON responses. The API includes a 'next' link in the response body for the next page. You need to follow these links until all pages are retrieved. Which approach is most appropriate using the requests library?

Accepted Answer

Use a while loop that sends a GET request to the current URL, parses the JSON, extracts the 'next' link, and updates the URL until 'next' is null.. When an API returns a 'next' link in the JSON body, the correct way to paginate is to iteratively follow that link. This requires parsing the JSON, extracting the URL, and making subsequent requests until the link is absent or null. The requests library facilitates this with its get() method and .json() parsing. Other options either misunderstand the features or assume a different pagination style.

Answer

Set the 'stream' parameter to True in the GET request to retrieve all pages in a single streaming response.

Answer

Use the requests.get() method with the 'params' argument to specify a page number, incrementing it until an empty response is received.

Answer

Use the requests.Session object and call session.get() with the initial URL, relying on the session to automatically follow the 'next' links in the JSON body.

Question 8

Which THREE of the following are recommended in PEP 8 for class definitions?

Accepted Answer

Put two blank lines between top-level classes.. Option A is correct because PEP 8's blank-lines rule requires two blank lines around top-level function and class definitions, so separating top-level classes with two blank lines is the recommended style. Option D is correct because PEP 8 prescribes the CapWords (CamelCase) convention for class names, e.g., class MyClass. Option E is correct because PEP 8 states that docstrings should be written for all public modules, functions, classes, and methods, so a class should include a docstring. Option B is not recommended: imports must be placed at the top of the file, after module docstrings and before module-level code, never inside a class body. Option C is not recommended: PEP 8 calls for docstrings on all public classes, and omitting them for private classes is not a PEP 8 rule.

Answer

Place imports inside the class definition.

Answer

Omit docstrings for private classes.

Question 9

A developer is implementing the Observer pattern and wants to store a list of observers without preventing them from being garbage collected when no other references exist. They decide to use `weakref.WeakSet` to hold the observers. Which statement accurately describes the behavior they should expect?

Accepted Answer

Observers are automatically removed from the set when their last strong reference is gone.. A `WeakSet` holds weak references and drops entries when the referenced objects are garbage collected. That makes it ideal for observer registries where you do not want the subject to keep observers alive. The other statements misstate weak reference semantics or confuse `WeakSet` behavior with `weakref.ref` dereferencing errors.

Answer

Observers continue to receive notifications until the `WeakSet` itself is garbage collected.

Answer

Calling `len()` on a `WeakSet` raises `ReferenceError` once any member is collected.

Answer

Observers must be hashable and are kept alive by the `WeakSet` until explicitly removed.

Question 10

You are designing a Tkinter application that uses a ttk.Treeview to display a table of records. You need to configure the widget so that users can select multiple non-contiguous rows and so that the first column shows a tree-style expander control. Which two actions must you perform? (Choose two.)

Accepted Answer

Set the show option to 'tree headings' or include 'tree' in the show tuple.. Multi-selection in a Treeview is governed by selectmode, which must be 'extended' to allow non-contiguous picks. The tree-style expander in the first column is controlled by the show option: including 'tree' (for example, 'tree headings') displays the tree column with expander controls. Heading text, height, and stretch are unrelated to these two requirements.

Answer

Call tree.heading('#0', text='Name') to set the label of the tree column.

Answer

Set the height option to a value greater than the number of rows.

Answer

Call tree.column('#0', stretch=True) to make the tree column resize with the widget.

Question 11

A developer is writing a Python script that processes sensitive data. They want to ensure that any errors are logged without exposing the sensitive data itself. Which logging practice should they follow to avoid leaking sensitive information in logs?

Accepted Answer

Use a custom logging filter to redact sensitive fields before logging.. Using a custom logging filter to redact sensitive fields is a balanced approach. It allows logging of useful information while preventing sensitive data from being written. This practice is recommended for applications handling sensitive data, as it maintains security without sacrificing debuggability.

Answer

Log only the exception type and not the message or traceback.

Answer

Disable logging entirely for the module that processes sensitive data.

Answer

Log the full exception traceback including the exception message.

Question 12

You are creating a simple Tkinter application and notice that your window does not appear on the screen after calling the Tk() constructor. Which method must be called to start the event loop?

Accepted Answer

root.mainloop(). The mainloop() method is required to start the Tkinter event loop, which listens for events and updates the display.

Answer

root.show()

Answer

root.render()

Answer

root.run()

Question 13

In the context of the Observer pattern, what is the benefit of an event-driven system over a direct-method-call approach?

Accepted Answer

Decoupling between the subject and observers.. Decoupling is the primary benefit; the subject does not need to know the implementation details of the observers.

Answer

Reduced memory usage.

Answer

Increased performance.

Answer

Automatic thread synchronization.

Question 14

A colleague built a Tkinter form where every Entry widget uses `pack()` in the same frame. They now need the labels to sit in a single column with the entries aligned in the next column and the whole form centered. They ask you to recommend the smallest structural change that makes this alignment reliable. What should you suggest?

Accepted Answer

Replace `pack()` with `grid()` inside a dedicated Frame, assigning labels and entries to the same row with different column indexes, then pack that Frame into the parent.. Grid is the correct tool for two-column alignment because it assigns widgets to explicit row and column cells, keeping labels and entries aligned regardless of content width. Wrapping the grid in its own Frame and packing that Frame into the parent is the smallest structural change that both aligns the fields and centers the form, without rewriting the entire window layout.

Answer

Keep `pack()` but add `side=tk.LEFT` to every label and `side=tk.RIGHT` to every entry so they form two implicit columns.

Answer

Use `pack()` for the labels and `grid()` for the entries in the same container, relying on Tkinter to merge both managers automatically.

Answer

Switch each Entry to `place()` and hard-code its x and y coordinates based on the current window size.

Question 15

You are implementing a Python client that communicates with a REST API over HTTPS. The API uses a self-signed certificate. You need to verify the server's certificate against a custom CA bundle while also ensuring that the hostname is verified. Which approach correctly configures the 'requests' library?

Accepted Answer

Set the 'verify' parameter to the path of the custom CA bundle; hostname verification is automatically enabled.. To use a custom CA bundle with requests, you pass the path to the bundle to the 'verify' parameter. This enables certificate verification against that bundle, and hostname verification is performed automatically as part of the SSL handshake. No additional parameter is needed for hostname verification, and disabling verification is insecure.

Answer

Set the 'verify' parameter to False and manually check the certificate fingerprint.

Answer

Set the 'cert' parameter to the path of the custom CA bundle and set 'verify' to True.

Answer

Pass the path to the custom CA bundle to the 'verify' parameter and set 'verify_hostname' to True.