2+2

4

5/0

---------------------------------------------------------------------------
ZeroDivisionError                         Traceback (most recent call last)
/tmp/ipykernel_2919626/2874912419.py in <module>
----> 1 5/0

ZeroDivisionError: division by zero

number = 42

text = "Hello, World"

notnumber = "42"

print(text)

Hello, World

print(number + 58)

100

print(number + notnumber)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
/tmp/ipykernel_2923490/2655672296.py in <module>
----> 1 print(number + notnumber)

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

print(7 + "cat")

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
/tmp/ipykernel_2923490/2564508834.py in <module>
----> 1 print(7 + "cat")

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

print(notnumber)
print(number)

42
42

type(notnumber)

str

newnumber = int(notnumber)
print(newnumber)
type(newnumber)

42

int

print(number+newnumber)

84

myfloat = float(newnumber)+0.5
print(myfloat)

42.5

my_list = [1, 2, 3, "four"]
print(my_list)

[1, 2, 3, 'four']

obj0 = 12
obj1 = "cat"
obj2 = ["a", "b", "c"]
my_list1 = [obj0, obj1, obj2]
print(my_list1)

[12, 'cat', ['a', 'b', 'c']]

my_list1.append("dog")
print(my_list1)

[12, 'cat', ['a', 'b', 'c'], 'dog']

my_list2 = ["cat", "dog", "parrot"]
print(my_list2[0])
print(my_list2[1])
print(my_list2[2])
print(my_list2[3]) #there's nothing here!

cat
dog
parrot

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
/tmp/ipykernel_2923490/2773750606.py in <module>
      3 print(my_list2[1])
      4 print(my_list2[2])
----> 5 print(my_list2[3]) #there's nothing here!

IndexError: list index out of range

my_list1[0:2]

[12, 'cat']

print(len(my_list1))

4

my_str = "The quick brown fox jumps over the lazy dog."
print(my_str[4])
print(my_str[4:9]) #4:9 indicates characters 4-8

q
quick

print(my_str[-4:])
print(my_str[:4])

dog.
The

["home", "away"][0][0:3]

'hom'

["home", "away"][0]

'home'

class_dict = {"course":"Python II", "location":"Davis Library", "time":"4pm"}
type(class_dict)

dict

print(class_dict["location"])

Davis Library

print(class_dict.keys())

dict_keys(['course', 'location', 'time'])

num=5
num<3

False

letter="a"
letter in ["a","b","c"]

True

num = 5
if num > 4:
    print("This number is greater than four")

This number is greater than four

num = 3
if num > 4:
    print("This number is greater than than four")
else:
    print("This number is less than or equal to four")

This number is less than or equal to four

num = 8
if num < 3:
    print("This number is less than three")
elif num < 10:
    print("This number is greater than or equal to three and less than ten")
else:
    print("This number is greater than or equal to ten")

This number is greater than or equal to three and less than ten

sales = [5, 2, 7, 9, 3]
total_sales = 0
total_sales = total_sales + sales[0]
total_sales = total_sales + sales[1]
total_sales = total_sales + sales[2]
total_sales = total_sales + sales[3]
total_sales = total_sales + sales[4]
print(total_sales)

26

my_nums = list(range(6))
print(list(range(6)))
for n in my_nums:
    print(n)

[0, 1, 2, 3, 4, 5]
0
1
2
3
4
5

#Nesting loops - indentation is key!
listOfWords = ["blue", "yellow", "red", "green"]
newList = [] #initialize an empty list

for color in listOfWords:
    numLetters = 0 #resets to zero each time the loop runs
    for letter in color:
        numLetters += 1
    temporaryList = [color, numLetters]
    newList.append(temporaryList)
    
print(newList)

[['blue', 4], ['yellow', 6], ['red', 3], ['green', 5]]

for number in range(10):
    if number % 2 == 0: 
    # % denotes the modulo operation - the result is the remainder after dividing by 2 
    # (i.e. 6%2 = 0, but 5%2 = 1)
        print(number)

scores=[95, 90, 66, 83, 71, 78, 93, 81, 87, 81]
grades=[]
for score in scores:
    if score >= 90:
        grade = "A"
    elif score >= 80:
        grade = "B"
    elif score >= 70 and score < 80:
        grade = "C"
    elif score >= 60 and score < 70:
        grade = "D"
    else:
        grade = "F"
    grades.append([score, grade])       
print(grades)

[[95, 'A'], [90, 'A'], [66, 'D'], [83, 'B'], [71, 'C'], [78, 'C'], [93, 'A'], [81, 'B'], [87, 'B'], [81, 'B']]

squares=[]
for n in range(1, 16):
    squares.append(n**2)
print(squares)

[1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, 169, 196, 225]

squares=[x**2 for x in range(1, 16)]
print(squares)

[1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, 169, 196, 225]

squaresdict={k:k**2 for k in range(1, 16)}
print(squaresdict)

{1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81, 10: 100, 11: 121, 12: 144, 13: 169, 14: 196, 15: 225}

sentence="the quick brown fox jumped over the lazy dog"
sentence=sentence.split(" ") #splits the string into a list with each space
print(sentence)
print([w for w in sentence if len(w)>4])

['the', 'quick', 'brown', 'fox', 'jumped', 'over', 'the', 'lazy', 'dog']
['quick', 'brown', 'jumped']

random_words=["statement", "toy", "cars", "shoes", "ear", "busy", 
              "magnificent", "brainy", "healthy", "narrow", "join", 
              "decay", "dashing", "river", "gather", "stop", "satisfying", 
              "holistic", "reply", "steady", "event", "house", "amused", 
              "soak", "increase"]

vowels=["a", "e", "i", "o", "u", "y"]

output=[]

for word in random_words:
    count = 0
    for char in word:
        if char in vowels:
            count = count + 1
    if count >= 3:
        output.append([word, count])

#1. Get or define the list my_numbers
my_numbers=list(range(100))

#2. Create an empty list for the new all-odd numbers, called my_numbers2.

#3. Use a loop to iterate through the list of numbers

    #3a. For a given number check to see if it is even.
    
    #3b. If the number is even, add 1.
    
    #3c. Append the resulting number to the my_numbers2 list.

user_ages=["34", "27", "54", "19", "giraffe", "15", "83", "61", "43", "91", "sixteen"]

ages = []
problems = []

for age in user_ages:
    try:
        a = int(age)
        ages.append(a)
    except:
        problems.append(age)
        
print(ages)
print(problems)

[34, 27, 54, 19, 15, 83, 61, 43, 91]
['giraffe', 'sixteen']

def mean(number_list):
    s = sum(number_list)
    n = len(number_list)
    m = s/n
    return m

numbers=list(range(1, 51))
print(mean(numbers))

25.5

Type	Example	Description
`int`	1, 2, 3	Integers (whole numbers)
`float`	1.5, 2.72, 3.14	Floating point numbers (decimals)
`str`	"cat", "dog", "car"	String, character, or text values
`list`	[1, 2, 3], ["cat", "dog"], [1, [2, 3]]	One or more objects indexed by order
`dict`	{"first_name":"John", "last_name":"Doe"}	One or more objects indexed by key values

Python: Introduction¶

Why Python?¶

Use Cases¶

Scripting¶

Natural Language Processing¶

Data Science¶

Others¶

Python vs. R¶

Python 2 vs. Python 3¶

Warning!

Getting Started¶

IDEs¶

Entering code¶

Don't be afraid of errors!¶

Data Types and Variables¶

Strings and Numbers¶

Getting help with functions¶

Lists¶

Indexing¶

Extra: Indexing beyond lists¶

Dictionaries¶

Review: Data Types¶

Flow Control¶

Conditions and Booleans¶

Conditional Statements¶

For Loops¶

Extra: Nested Loops¶

For Loops with Conditionals¶

Comprehensions¶

Review¶

Pseudocode and Comments¶

Pseudocode¶

Comments¶

Try / Except - Robustness¶

User-defined Functions¶

Getting Ready¶

Questions?¶

References and Resources¶