# Salvatore Lopiparo

Software Engineer

# Super Simple Python #5 – True, False, and The if Statement

If you run out of money, then don’t spend money.

Please, keep that in mind. (Not just for this lesson…)

Note: In this lesson and in most future lessons, we will be writing functions that span several lines. It will be easier to write the lines into a file, then copy-paste them into the Python Console. From within PyCharm, go to File>New>Python File, then name it “lesson5”. Use that as a place to write functions for this lesson. Now to the programming!

If this is your first time here, I recommend looking at the first lesson. Starting there and going through the rest of the lessons will prepare you to go through this more advanced lesson!

First, `True` and `False` are used in Python to denote whether something is… well, true or false. Here’s your basic Truth Table:

```1 < 2 - True (1 is less than 2)
1 > 2 - False (1 is greater than 2)```

Since 1 is NOT greater than 2, you’ll get `False`. Here are the rest (for reference. We’ll use them more later):

```1 == 1 - True (1 is equal to 1, note the double equal signs)
1 == 2 - False (1 is equal to 2)

1 != 1 - False (1 is NOT equal to 1)
1 != 2 - True (1 is NOT equal to 2)

1 <= 2 - True (1 is less than OR equal to 2)
1 <= 1 - True (1 is less than OR equal to 1)
2 <= 1 - False (2 is less than OR equal to 1)

1 >= 2 - False ( 1 is greater than OR equal to 2)
1 >= 1 - True (1 is greater than OR equal to 1)
2 >= 1 - True ((2 is greater than OR equal to 1)

(x.x) o-(''Q) - Boxing Kirby```

`if statements` work like this:

If some value is True, then do some action.

So in Python, we would write something like the following. Note the 4 space indent similar to a function:

```>>> if True:
...     print('It was True!')
...
It was True!
>>> if False:
...     print("It was True!")
...
```

Or something a bit more useful:

```>>> my_money = 100
>>> if my_money > 10:
...     print('Yay! I have money to spend: ' + str(my_money))
...     my_money = my_money - 10
...     print('I just spent \$10!')
...     print('This is how much money I have left: ' + str(my_money))
...
Yay! I have money to spend: 100
I just spent \$10!
This is how much money I have left: 90```

We can also add a different statement afterwards, called `else`, that will handle when the `if statement` didn’t happen:

If some value is True, then do some action, otherwise (else) do some other action.

```>>> if False:
...     print("It was True!")
... else:
...     print("It was False!")
...
It was False!```

Or back to our more useful code:

```>>> if my_money > 10:
...     print('Yay! I have money to spend: ' + str(my_money))
...     my_money = my_money - 10
...     print('I just spent \$10!')
...     print('This is how much money I have left: ' + str(my_money))
... else:
...     print("I don't have enough money!!")
...     print('I\'m poor now: ' + str(my_money))
...
Yay! I have money to spend: 90
I just spent \$10!
This is how much money I have left: 80```

Let’s put that in a function:

```def spend_money(money_in_bank, money_to_spend):
if money_in_bank > money_to_spend:
print('Yay! I have money to spend: ' + str(money_in_bank))
money_in_bank = money_in_bank - money_to_spend
print('I just spent \$' + str(money_to_spend) + '!')
print('This is how much money I have left: ' + str(money_in_bank))
else:
print("I don't have enough money!!")
print('I\'m poor now: ' + str(money_in_bank))
return money_in_bank```

Here, we’re replacing the \$10 with `money_to_spend` so we can change how much we spend. Don’t forget the return statement at the end!

Now let’s go on a shopping spree!

```>>> my_money = spend_money(my_money, 40)
Yay! I have money to spend: 80
I just spent \$40!
This is how much money I have left: 40

>>> my_money = spend_money(my_money, 20)
Yay! I have money to spend: 40
I just spent \$20!
This is how much money I have left: 20

>>> my_money = spend_money(my_money, 300)
I don't have enough money!!
I'm poor now: 20```