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					<h1>Intro to Python Workshop</h1>
					<p>
						<small>
							Presented by:  <br><br>
							Jennifer Reiber Kyle / <a href="http://twitter.com/jreiberkyl" target="blank">@jreiberkyle</a> 
							<br>and <br>
							<a href="http://iowatechchicks.com" target="blank">Iowa Tech Chicks</a> / <a href="http://twitter.com/iowatechchicks" target="blank">@iowatechchicks</a>
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					<br>
					<p><small>
						<b>Slides Source:</b>
						<a href="https://github.com/jreiberkyle/intro-to-python" target="blank">
						https://github.com/jreiberkyle/intro-to-python
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### Part 2: Advanced Control

 - Loops
 - Data Structures
 - Hangman Game!
 - Functions
 - Modules

---

## Loops

- So far our code has run from top to bottom
- Programs usually need to do something over and over agin
- Computers don’t mind doing repetitive tasks

---

## While Loop
```python
#"while" something is true
#perform an action
while True:
	print 'yep'
	ret = raw_input('continue? (y/n)')
	if 'y' == ret:
		break
```

Try it out!

---

Code within the loop may invalidate the condition
```python
loop = True
while loop:
	print 'Are we there yet?'
	loop = False
print 'Done the loop'
```

Try it out!

---

To run a certain number of times we test a
variable and increment within the loop
```python
x = 1
while x < 10:
	print x
	x += 1
```
Try it out!

---

## Exercise

Print from 10 to 1

---

```python
x = 10
while x > 0:
	print x
	x -= 1
```

---

## Exercise

Guess a Number

- We’re going to write a game for the computer
- The computer will pick a number and we have to guess it
```
from random import rand
int x = randint(1,10)
```
- The user should know if they are too high or too low
- We know how to ask for input
- We know how to compare guesses
- We want to give the user multiple chances

---

```python
from random import randint
x = randint(1,10)
print "I'm thinking of a number between 1 and 10"

correct = False

while not correct:
    guess = raw_input("Guess the number\n")
    guess = int(guess)
    if guess > x:
        print 'Too high'
    elif guess < x:
        print 'Too low'
    else:
        print "You're right!"
        correct = True
```

---

## Data Structures

- [Lists](https://docs.python.org/2/tutorial/introduction.html#lists)
 - An ordered set of objects
 - Lists can hold strings, integers, floats, booleans, and 
anything else you can create

---

## Creating Lists
```python
mylist = [1,2,3,4]
print mylist #[1, 2, 3, 4]
companies = ['My Elephant Brain', 're:3D', 'Hacker You']
print companies
#['My Elephant Brain', 're:3D', 'Hacker You']
kitchen_sink = [1 , 'a', True]
print kitchen_sink
#[1, 'a', True]
```

---

## Accessing Items in a List

```
>>> companies = ['My Elephant Brain', 're:3D', 'Hacker You']
['My Elephant Brain', 're:3D', 'Hacker You']
>>> companies[1]
're:3D'
>>> companies[-1]
'Hacker You'
>>> companies[10]
Traceback (most recent call last): File "<stdin>",
line 1, in <module>
IndexError: list index out of range
```

---

## Exercise
- Using a list and a while loop, print the days of the week
- ‘break’ the loop on Wednesday

---

### Modifying a List

```python
l = []
#add an item
l.append(5)
print l
#remove an item
l.remove(3)
print l
# remove throws an error if the item does not exist
l.remove(9)
```

---

## A Quick jump Back to Loops
```python
# for loops make it easy to loop over a list
for company in companies:
    print company
# they are also useful for looping
# a known number of times
for i in range(1,10):
	print i
```

---

## Exercise

- Use a for loop to print the days of the week
- Use a for loop to count from 10 to 1
 - Hint: by default `range()` increases by 1 each time, but you can give it a third
argument to tell it the number to increment by each time
 - e.g. `range(0, 10, 2)`

---

## More data structures...
- Sets
 - Like lists, but (1) unordered and (2) only store unique elements
- Tuples
 - Like lists, but cannot change after creation
- Dictionaries
 - Unordered list indexed by keys
```python
my_dict = {
	'name': 'Jennifer Reiber Kyle',
	'group': 'Iowa Tech Chicks'}
```

---

# Hangman Game!
(credit: Python Programming for the Absolute Beginner)

**Keep in Mind:**

- Before coding, think about what you’re trying to do.
- Computers need specific instructions, so you need to
break it down.
- You can start by playing hangman on paper with each other.

---

### Hint: 

- Create a list of hangman 'states'

```python
HANGMAN = [
"""
------
|    |
|
|
|
|
|
|
|
------
""",
...
]
```

---

### Hint: 

- Create a list of words
- Pick the secret word:
 - `random.choice(WORDS)`

- Track the number of wrong guesses
- Track the letters used
- Create a string that tracks the correct guesses
 - One dash for each letter in the secret word:
  - `so_far = "-" * len(word)`
 - For each correct guess, place the letter in its correct spot

---

### Solution

[https://github.com/jreiberkyle/intro-to-python/blob/master/examples/hangman_soln.py](./examples/hangman_soln.py)

---

# Functions
We put reusable code inside 'functions'


```
def add_two(a, b):
    return a + b

ans = add_two(1, 2)
print ans
```

---

## Exercise

Write functions to do the following

- Multiply two numbers
- Combine an int and a string
- Print the sequence of a given number, down to zero
 - 5, 4, 3, 2, 1, 0

---

## Modules (local)
Python code is reusable by other code

functions.py
```
def add_two(a, b):
    return a + b
```

start python in the same folder as functions.py

```
from functions import add_two
print add_two(1,2)
```

---

## Python Libraries

One of the greatest aspects of Python is the large number of libraries

Some useful libraries:

- numpy (used at Planet Labs to process images as arrays)
- scipy
- scikit-learn

---

### You’re programmers now!
- Sure there’s more to know
- There’s always more to know
- The trick is using what you know
- More Resources
 - http://www.pyschools.com/	
 - http://www.djangobook.com/en/2.0/index.html
 - http://learnpythonthehardway.org/

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				<h1>Thank You!</h1>
				<br>
<p>Support Iowa Tech Chicks at <a href="http://www.iowatechchicks.com/support/">iowatechchicks.com/support</a></p>
<br>
<p>Connect with me  on Twitter (@jreiberkyle) or Github (github/jreiberkyle)</p>
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