Week 4 Refresher¶
Let’s refresh your memory! First, read the reminders about syntax. Then, complete the exercises!
Reminders¶
Basic Variables and Operations¶
There are four basic variable types
1 2 3 4 | x = 5 # int
x = 5.0 # float
x = "5" # str
x = True # bool
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You can convert between types
1 2 3 4 | y = "5" # a string variable
x = int(y) # convert to integer
x = float(y) # convert to float
z = str(x) # convert the float to string. does this equal "5" or "5.0"
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There are 7 math operator types
1 2 3 4 5 6 7 8 9 | x = 10
y = 2
x + y
x - y
x * y
x / y
x // y
x ** y
x % y
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There are shortcuts for math operators. The following pairs of statements have the same result.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 | x = 5
y = 3
# x = x + y
x += y
x = 5
y = 3
# x = x - y
x -= y
x = 5
y = 3
# x = x * y
x *= y
x = 5
y = 3
# x = x / y
x /= y
x = 5
y = 3
# x = x // y
x //= y
x = 5
y = 3
# x = x ** y
x **= y
x = 5
y = 3
# x = x % y
x %= y
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Booleans and Comparisons¶
There are boolean variables
1 2 | x = True
x = False
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Variables can be compared to create boolean variables
1 2 3 4 5 6 7 8 | x = 42
y = 41
x == y
x != y
x > y
x >= y
x < y
x <= y
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Boolean variables can be combined using the special boolean keywords
1 2 3 4 5 6 | x = True
y = False
z1 = x and y
z2 = x or y
z3 = (x and y) or (not x and not y)
z4 = (not x and y) or (x and not y)
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Code blocks let you group code. In python, they are created with 4 spaces.
In pycharm and most python editors, hitting tab will just add 4 spaces.
if
statements use code blocks.
1 2 3 4 | x = 10
y = 9
if x > y:
print("X is bigger!")
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if
statements can be expanded using elif
.
elif
will only be used if the first if
is false.
(hidden question: What needs to be put into the placeholder to make the above code work?)
1 2 3 4 5 6 7 8 9 10 | x = "3"
# placeholder
if x == 1:
print("x is 1")
elif x == 2:
print("x is 2")
elif x == 3:
print("x is 3")
else:
print("I'm not sure what x is")
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Getting Input from Users¶
You can use the input
to get information from the user.
Try the following. What is missing?
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | print("My Menu: ")
print("\t 1. Option 1")
print("\t 2. Option 2")
print("\t 3. Option 3")
x = input("What option do you choose?")
# placeholder
if x == 1:
print("x is 1")
elif x == 2:
print("x is 2")
elif x == 3:
print("x is 3")
else:
print("I'm not sure what x is")
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