PCPP1 Practice Test 14 — 15 Questions

Question 1

You are placing several widgets in a window using the grid() geometry manager and want a widget to span multiple columns in the same row. Which grid() option accomplishes this?

Accepted Answer

columnspan. In grid(), the columnspan option specifies how many columns a widget should occupy, starting from its column index. This is the mechanism for horizontal spanning within a row. rowspan handles vertical spanning, sticky controls alignment and stretching inside the cell, and ipadx adds internal padding. Combining columnspan with sticky lets a widget both cover several columns and fill the resulting space as desired.

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ipadx

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rowspan

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sticky

Question 2

You are building a canvas-based drawing tool and need to detect when the user clicks on a specific rectangle item to select it, while other clicks should be ignored. Which canvas feature should you use?

Accepted Answer

Use the canvas tag_bind() method to bind <Button-1> to the rectangle's tag or item id.. Canvas items support their own event bindings through tag_bind(), which ties a callback to a tag or item id. When the user clicks, the canvas performs hit testing and invokes the binding only if the pointer is over a matching item, honoring stacking order for overlaps. This is more robust than comparing raw coordinates and automatically tracks items as they move or change, making it the correct choice for selecting individual shapes.

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Call itemconfigure() on the rectangle with an activefill option to detect selection.

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Bind <Button-1> to the top-level window and use the focus() method to determine which item was clicked.

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Bind a <Button-1> handler to the canvas and compare event coordinates against the rectangle's bounding box.

Question 3

You are building a client for a REST API that requires an OAuth 2.0 bearer token. The token is long-lived and stored in an environment variable. You want every request in a session to carry the Authorization header without repeating the header setup at each call site. Which approach is correct and idiomatic with the requests library?

Accepted Answer

Create a requests.Session, set session.headers.update({'Authorization': f'Bearer {token}'}), and issue calls through that session.. A Session stores default headers that are merged into each prepared request, so updating session.headers with the Authorization bearer value applies authentication everywhere the session is used. Environment variables are not consulted by requests for outgoing headers, tuple-based auth produces Basic credentials, and overriding send is needlessly complex compared with the supported header mechanism.

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Pass auth=('Bearer', token) to each request so the library builds the header.

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Set os.environ['HTTP_AUTHORIZATION'] = f'Bearer {token}' before each call.

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Subclass requests.Session and override send to inject the header after the request is prepared.

Question 4

You are maintaining a Tkinter inventory application where users type quantities into an Entry widget. A colleague reports that the application accepts "12.5" for an item that must be a whole number, and invalid keystrokes are only caught after the user clicks Save. You must reject non-numeric input as it is typed, while still allowing a normal editing experience. Which mechanism should you register on the Entry widget?

Accepted Answer

A command callback passed to the Entry widget's validatecommand option, with validate set to "key".. Tkinter's Entry validation framework invokes a registered callback at defined moments, and validate="key" triggers it on every keystroke before the change is applied. Returning False from that callback cancels the edit, so non-integer characters are rejected immediately while legitimate editing continues to work. This is the only listed approach that prevents bad input from ever reaching the widget, matching the stated requirement.

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A call to the Entry widget's config method with the state option set to "readonly" while the user is typing.

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A trace callback attached to a StringVar linked to the Entry widget, raising an exception whenever the new value is not an integer.

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A binding for the <Return> event that inspects the Entry contents and shows a messagebox when the value is not an integer.

Question 5

Your team uses a REST API that requires a Bearer token in the Authorization header for every request. You want to configure a `requests.Session` so that all requests made through it automatically include this header, and you also want to reuse the underlying TCP connection across calls. Which approach is correct?

Accepted Answer

Create a Session, set session.headers.update({'Authorization': 'Bearer ' + token}), and use session.get() for subsequent calls.. A requests.Session maintains a connection pool and a persistent set of headers. Setting the Authorization header once on the session applies it to all requests made through that session, and the underlying urllib3 connection pool reuses TCP connections for the same host. This satisfies both the authentication and connection reuse requirements.

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Set requests.default_headers['Authorization'] = 'Bearer ' + token and call requests.get(url).

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Call requests.get(url, headers={'Authorization': 'Bearer ' + token}) for every request.

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Create a Session and pass auth=('Bearer', token) to session.get() on each call.

Question 6

A Tkinter application uses a Canvas to draw a seating chart. Each seat is a rectangle created with create_rectangle, and seats are grouped by section. When a section is selected, every seat in it must change fill color, and some seats must later be moved to a new position. Which strategy best supports efficient grouped updates while keeping individual seats addressable?

Accepted Answer

Assign a unique tag to each seat's rectangle and use the tag to call itemconfig on all seats in the section, and use coords or move to reposition individual seats.. Canvas tags are the intended mechanism for applying an operation to many items at once: itemconfig with a tag recolors every matching item in a single call, and each seat can also carry a unique tag for precise coords or move operations. This yields efficient section-wide updates while preserving individual addressability, unlike per-item loops or destructive recreation.

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Delete all rectangles in the section and recreate them with the new color and position whenever a section changes.

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Place each seat rectangle inside its own Frame widget and change the Frame background color, relying on the canvas window items to reflect the change.

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Store each rectangle's item id in a dictionary and iterate over the section, calling itemconfig and coords on each id individually.

Question 7

You are writing a Python client to consume a REST API. The API documentation states that the server may respond with a 307 Temporary Redirect when a resource has moved temporarily. You need to ensure that your client, built with the 'requests' library, preserves the original HTTP method and body when following such redirects. Which of the following best describes how 'requests' handles a 307 redirect by default?

Accepted Answer

It automatically re-sends the request with the same method and body to the new URL.. When 'requests' encounters a 307 Temporary Redirect, it follows the redirect while preserving the original HTTP method and request body, as mandated by the HTTP specification. This ensures that non-idempotent requests like POST are not inadvertently converted to GET, which could lead to data loss or unintended side effects. The library handles this automatically unless redirects are disabled.

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It changes the request method to GET and discards the body.

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It returns the 307 response directly without following the redirect.

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It raises a 'TooManyRedirects' exception immediately.

Question 8

You have a Button widget and want to trigger a function named 'process_data' when the user clicks it. Which is the standard way to associate the function with the button?

Accepted Answer

button = Button(root, command=process_data). The 'command' parameter is the standard way to bind a callback function to a button click event.

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button = Button(root, event=process_data)

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button.bind('<Button-1>', process_data)

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button.set_action(process_data)

Question 9

When receiving data from a TCP socket using 'recv(buffer_size)', what does the returned value represent?

Accepted Answer

The data as a byte string. The method returns the bytes received, up to the specified buffer size.

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A boolean indicating connection status

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The total number of bytes in the stream

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The number of packets received

Question 10

A script processes data from untrusted sources. Which technique best mitigates 'pickle' deserialization vulnerabilities?

Accepted Answer

Use an alternative format like JSON or XML for serialization.. The pickle module is inherently unsafe for untrusted data because unpickling executes arbitrary code via the __reduce__ method during object reconstruction. The only reliable mitigation is to avoid pickle entirely for untrusted input and use a data-only format like JSON or XML, which cannot execute code during parsing. JSON/XML parsers only construct primitive data types (dicts, lists, strings, numbers), eliminating the remote code execution vector.

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Only unpickle from files with a specific extension.

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Wrap the unpickling in a try-except block.

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Use 'pickle.load()' with a restricted whitelist of modules.

Question 11

What is the primary function of the 'bg' parameter in a widget configuration?

Accepted Answer

Sets the background color.. In widget configuration (as used in Python GUI frameworks such as Tkinter and similar toolkits), the 'bg' parameter is the standard abbreviation for 'background', and it sets the background colour of the widget. It accepts colour names (e.g., 'red', 'blue') or hexadecimal colour codes (e.g., '#FF0000').

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Sets the button group.

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Sets the border group.

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Sets the base grid.

Question 12

When writing a library, what is the best practice for documenting the usage of a function?

Accepted Answer

Use docstrings to provide a clear summary and usage details.. Docstrings provide the most standard and accessible form of documentation that can be integrated with tools like Sphinx.

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Include the documentation as comments above the function definition.

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Provide usage examples in the 'README.md' file only.

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Wait for users to ask for documentation.

Question 13

Which THREE practices are recommended when handling external libraries?

Accepted Answer

Use a virtual environment for every project.. Option C is correct because creating a virtual environment (e.g., python -m venv .venv) for every project isolates its third-party packages from the system Python and other projects, preventing version conflicts and keeping the global interpreter clean. Option D is correct because documenting dependencies in a manifest file (such as requirements.txt, pyproject.toml, or package.json) records exactly which external libraries the project needs, enabling reproducible installs and easier auditing. Option E is correct because pinning dependencies in requirements.txt (e.g., requests==2.31.0) locks exact versions so builds are deterministic and a later upstream release cannot silently break the application. Option A is wrong because installing libraries globally pollutes the system interpreter, risks version clashes between projects, and often requires elevated privileges. Option B is wrong because imports should be grouped at the top of the file per PEP 8, and deferring them to the end harms readability and can cause NameError at runtime.

Answer

Install libraries globally.

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Import all libraries at the very end of the file.

Question 14

When using sqlite3.Row, what is the primary benefit over using a standard tuple?

Accepted Answer

It provides dictionary-like access to columns by name.. sqlite3.Row allows accessing column values by name (string keys) instead of just numerical indices.

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It automatically commits transactions.

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It is faster to execute.

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It supports multi-threading natively.

Question 15

You have a Checkbutton and you need to track its state. What is the recommended way to associate a variable with the Checkbutton?

Accepted Answer

Pass a BooleanVar object to the 'variable' parameter.. A BooleanVar or IntVar should be passed to the 'variable' parameter of the Checkbutton.

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Use the 'onvalue' parameter.

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Use the state attribute directly.

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Use the 'command' parameter to set a global flag.