Python Arrays and For Loops

Here's some pre-written JavaScript functions. Your job is to practice Python by converting these functions from JavaScript to Python.

Each of the Python files has the function definitions that you're expected to write. All of the functions have the Python keyword pass inside the functions. pass simple means "do nothing" and allows methods to maintain proper indentation.

You should delete pass when you write the function and replace it with your own code.

Running Solutions

Run the original JavaScript files with node, and run your Python solutions with python3 both in your terminal. Look at the output and make sure they print out the same things:

node fileName.js
python3 file_name.py

Scroll down to the end of this readme to see an advanced bash trick you can use to run all .js programs and .py programs in your current directory.

Common Errors

You may run into some errors along the way. If you find an error try to google for a solution. There should be some good Stack Overflow results for the things we're trying to do.

Here are several commong errors I expect you to run into:

IndexError: list index out of range

This means you accessed an array at an index beyond the number of things it has.

a = [1,2,3]
print(a[99])

TypeError: unsupported operand type(s) for +: 'int' and 'str'

Python won't automatically concatenate numbers and strings. You'll have to pass a number through the str() function to manually convert it to a string and get concatenation to work.

"my favorite number is " + 1

"my favorite number is " + str(1)

Or, use f-strings!

f"my favorite number is {1}"

SyntaxError: invalid syntax def a()

Remember to append a colon at the end of a line when you define a function:

def print_hello()
  print("hello!")

def print_hello():
  print("hello!")

IndentationError: expected an indented block / unexpected indent

Python is very, very particular about indendation. It literally uses indentation to detect where functions begin and end. If you don't maintain perfect indentation your code will not run.

You have some freedom. You can use tabs, two-spaces, or four-spaces or whatever you like for your indentation. Python only requires that you be consistent.

Bad

def print_hello():
print("hello!")

def print_hello()
  print("hello!")
    print("hello!")

Good

def print_hello():
  print("hello!")
  print("hello!")

Bash Magic

Your terminal uses a shell called bash. Bash is a scripting langauge that has it's own way to write for loops, create variables, run if statements and create variables. In your career as a programmer you'll naturally pick up more and more bash, just like you're already familiar with common commands like ls, cd, and mkdir.

You can copy and paste these pieces of code and run them in your terminal. The commands list all the files that have a .js or py extension and run them with either node or python3. Running these for loops is a good way to quickly check how your Python output compares to your JavaScript output when you're all done.

for JS in `ls *.js`
do
node $JS
done

for PY in `ls *.py`
do
python3 $PY
done

Licensing

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