1. 4.3
a. "boolean".capitalize()

b. "C02 H20".find("2") # make sure to put the 2 in quotes.  it's a string, not a number

c. 
temp = "CO2 H20"
temp.find("2", temp.find("2") + 1)

find can be called with a single parameter or with two parameters, where the first is a 
string and the second an int representing the index to start searching from.  The example
above starts looking for "2" at the index:

temp.find("2")+1

which is one after the index it found the first occurrence at.

Another way of doing this is:

temp.find("2", 3)

Though this assumes that you precomupted the index of the first occurrence.

d. 'Boolean'[0].islower()

Gets the first character of the string and then checks to see if it is lowercased.

e. 'MoNDaY'.lower().capitalize()

Notice that you can chain these together.

f.  " Monday".strip()

2.
def last_half(string):
    return string[len(string)/2:]

This rounds down and therefore for a longer last half.