When you write a variable with two underscores like __age, Python changes its name internally to _ClassName__age, this is called name mangling, it is used to avoid accidental override in child classes, it does not make the variable truly private, but it helps prevent mistakes in inheritance. A virtual environment keeps project libraries separate from system Python, this avoids version conflicts, you create it using the venv module, then activate it before running or installing packages, this is very common in scripting and automation. Environment variables are used to store things like API keys, paths, and config values, in Python you read them using the os module, this keeps secrets out of code, it is very common in deployment and automation scripts, and you can also set default values if the variable is missing. /usr/bin/env python3 it means use whatever python3 is available in the user’s environment, this makes the script more portable across systems, without a shebang you would always have to type python script.py, but with it you can run the file directly. You read the file line by line instead of loading all at once, update a counter for each word, and keep track of the current most frequent word, this avoids memory issues for big files.
- Playwright handles browser automation and testing by providing a high-level API that interacts directly with browser engines like Chromium, Firefox, and WebKit.
- A Primary Key is a column or set of columns that uniquely identifies each record in a table.
- # Auto-merge schema when writing (adds new columns automatically) df_with_new_column.write \ .format(“delta”) \ .option(“mergeSchema”, “true”) \ .mode(“append”) \ .save(“/path/to/delta-table”)
The list provides get() method to get the element at a specified index. Map implementation classes are HashMap, HashTable, TreeMap, ConcurrentHashMap, and LinkedHashMap. The map allows a single null key at most and any number of null values. Once we have the index of the first element, we can return count as n – index of the first zero. Count the ZerosSince the input array is sorted, we can use Binary Search to find the first occurrence of 0.
A stack is a data structure that performs three operations, push, pop and peek, even though the last one is not as common. Developing debugging techniques and getting comfortable locating subtle mistakes within code are extremely useful skills which go beyond just writing working solutions. For more specialized functions with complex parameters, most interviewers allow quick reference checks. For common operations like creating a DataFrame, using groupby, or writing list comprehensions, interviewers generally expect you to code from memory. PySpark is a distributed computing framework that processes data across a cluster of machines, allowing you to handle datasets too large for a single server. The built-in open() function is the most common example, but in data engineering you’ll often need to write your own for database connections, temporary files, or resource locks.
It is the full entry point for browser management, test generation, debugging, and report viewing. The CLI https://uvik.io/ saves artifacts (YAML accessibility snapshots, screenshots, trace files) to disk rather than loading them into an LLM’s context window. MCP gives the model the accessibility tree as structured YAML, so it sees roles, labels, and states the same way getByRole does. Playwright MCP (Model Context Protocol) is the standardized bridge between large language models and a live Playwright browser session. Each shard runs a subset of the tests, and the results are merged at the end.
The built-in garbage collector keeps track of all objects and frees up memory by removing those that are no longer in use. Roles like senior systems engineer or technology analyst fall in this bracket, with average salaries ranging from ₹6 LPA to ₹10 LPA, depending on skills and project exposure. When using with, the resource is automatically cleaned up once the block of code is executed, even if an error occurs. In production, I integrate tools like Sentry and New Relic to monitor errors and performance metrics continuously.