human
Here each fragment is doing given the following:
2. Python
Python is the main programming language we'll use in this course.  We assume you have some experience with Python or can learn it yourself, but here is a brief review.
Below are some simple Python program fragments.
You should feel confident explaining what each fragment is doing. If not,
please brush up on your Python. There a number of tutorials online (search
for "Python tutorial"). https://docs.python.org/3/tutorial/ is a good place to
start.
assistant
#Here each fragment is doing.
2 + 2

# This is a comment.
# In Python, the ** operator performs exponentiation.
math.e**(-2)

print("Hello" + ",", "world!")
"Hello, cell output!"

def add2(x):
    """This docstring explains what this function does: it adds 2 to a number."""
    return x + 2

def makeAdder(amount):
    """Make a function that adds the given amount to a number."""
    def addAmount(x):
        return x + amount
    return addAmount

add3 = makeAdder(3)
add3(4)

# add4 is very similar to add2, but it's been created using a lambda expression.
add4 = lambda x: x + 4
add4(5)

sameAsMakeAdder = lambda amount: lambda x: x + amount
add5 = sameAsMakeAdder(5)
add5(6)

def fib(n):
    if n <= 1:
        return 1
    # Functions can call themselves recursively.
    return fib(n-1) + fib(n-2)

fib(4)

# A for loop repeats a block of code once for each
# element in a given collection.
for i in range(5):
    if i % 2 == 0:
        print(2**i)
    else:
        print("Odd power of 2")

# A list comprehension is a convenient way to apply a function
# to each element in a given collection.
# The String method join appends together all its arguments
# separated by the given string.  So we append each element produced
# by the list comprehension, each separated by a newline ("\n").
print("\n".join([str(2**i) if i % 2 == 0 else "Odd power of 2" for i in range(5)]))