Dead Simple Python

Question 1

How to quit the interactive Python session?

Answer 1

exit()

Question 2

Two steps to open a venv project of python?

Answer 2

1. open the project containing env directory.
2. set the python interpreter from terminal (bash/cmd/powershell).

Question 3

how to check which python interpreter is currently active in my venv?

Answer 3

1. where python (windows)
2. which python (Linux/macOS)

Question 4

How to activate the python interpreter of the venv from terminal?

Answer 4

1. For bash, type:
   source ./Scripts/activate
2. For cmd, type: .\Scripts\activate.bat
3. For powershell: .\Scripts\activate.ps1

Question 5

If trying to activate Python interpreter results in permission error in powershell (scripts not allowed to execute), then what to do?

Answer 5

Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser

Question 6

How to leave the virtual environment of Python?

Answer 6

1. For powershell: deactivate
2. For cmd: .\Scripts\deactivate.bat
3. For bash: deactivate

Question 7

Create a virtual environment in Python by the name “myenv”.

Answer 7

python3 -m venv myenv

It creates a myenv/ directory in the current working directory.

Question 8

To run a Python module from CLI, it must have _ .

Create a module that displays your name and run it from CLI using -m flag

Answer 8

“__main__” entry point.

\_\_name\_\_ == '\_\_main\_\_'

Question 9

How to print the module name (mytool) when running the module using
python -m mytool command

Answer 9

print(sys.argv[0])

Question 10

What is a positional argument in python CLI?
How is it different from other (optional) arguments?

Answer 10

Positional argument
* doesn’t use --.
* is required by default.
* Order matters.

Non-positional argument
* starts with -- or -.
* often has a default value
*

Question 11

CLI command:
python -m mymodule coffee --name Sahil

CLI output:
searching coffee for Sahil

Answer 11

def main():
parser = argparse.ArgumentParser(description="Search items for you")
    parser.add_argument(
        "itemname", 
        help="item to search for",
        nargs="?",
        default="coffee"
    )
    parser.add_argument("--name", help="Your name", required=True)
    argsObject = parser.parse_args()
    print(f"Searching {argsObject.itemname} for {argsObject.name}...")

Question 12

How to specify that argument is optional, i.e., at most one (0 or 1) argument is allowed, while adding argument to ArgumentParser?

Answer 12

nargs

parser = argparse.ArgumentParser()
parser.add_argument(
  "--foo", 
  nargs="?", 
  default="value"
)

Question 13

What are lazy imports in Python?

Answer 13

Importing modules inside a function or conditionally, makes the import lazily evaluated.

def process_data():
    import pandas as pd

Question 14

As best practice, keep imports scoped to the respective modules and entrypoint of the application lean.
What is entrypoint of a Python application?

Answer 14

main.py

Imports like pandas are inside run_app, which

Question 15

main.py contains following code:

if \_\_name\_\_ == "\_\_main\_\_":
    run_app()

The run_app() function contains import to pandas. During during container startup with CMD ["python", "main.py"] , will the pandas module be loaded?

Answer 15

No.
pandas is only loaded when run_app() is called — not during container startup.

Question 16

Python normally doesn’t allow breaking a statement across lines unless inside parentheses, brackets, or braces.
Wrapping the chaining call of functions inside _ lets you split it neatly across multiple lines

Answer 16

parentheses
(…)

Everything inside the parentheses is treated as one single expression. Without parentheses, you’d need ugly backslashes \ for line continuation.