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# Coding Club 
## week 2

---

# Recap

1. Variables
2. Functions

---

# Variables

Last time we got to talk about two different variables types

## integers

example:

```python
    radius = 1
    pi = 3.1415926535
    print pi * r ** 2
```
output:

9.86960437853

---

# Variables

Last time we got to talk about two different variables types

## integers

example:

```python
    radius = 1
    pi = 3.1415926535
    print pi * r ** 2
```
```
    9.86960437853
```

## strings

example:
```python
    greeting = "Hello World!"
    print greeting
```
```
    Hello World!
```

---

# Functions

Last time we also talked about some "built-in" functions

---

# Functions

Last time we also talked about some "built-in" functions
## raw\_input()

example:
```python
    print "What is your name? "
    name = raw_input()
    print "Hello ", name
```
```
    What is your name?
    > Mark
    Hello Mark
```

---

# Functions

Last time we also talked about some "built-in" functions
## raw\_input()

example:
```python
    print "What is your name? "
    name = raw_input()
    print "Hello ", name
```
```
    What is your name?
    > Mark
    Hello Mark
```

## math.sqrt(number)

example:
```python
    import math
    print "Say something irrational"
    print math.sqrt(2)
```
```
    Say something irrational
    1.41421356237
```

---

# User Defined Functions

Finally we talked about defining your own function

---

# User Defined Functions

Finally we talked about defining your own function
```python
import math
def pythag(a, b):
    return math.sqrt(a ** 2 + b ** 2)
```

---

# User Defined Functions

Finally we talked about defining your own function
```python
import math
def pythag(a, b):
    return math.sqrt(a ** 2 + b ** 2)
```
Here we define a function called `pythag` with "arguments" `a` and `b`

---

# User Defined Functions

Finally we talked about defining your own function
```python
    import math
    def pythag(a, b):
        return math.sqrt(a ** 2 + b ** 2)
```
Here we define a function called `pythag` with "arguments" `a` and `b`

Remember that the `return` keyword specifies the value that the function 
evaluates to

---

# This Time
- String Manipulation
- Lists
- Putting Them Together

---

# String Manipulation (Interpolation)

## Idea
Suppose that during your python program you wanted to insert a string in the middle of another string

"One day             went to the store"

---

# String Manipulation (Interpolation)

## Idea
Suppose that during your python program you wanted to insert a string in the middle of another string

"One day Mark went to the store"

---

# String Manipulation (Interpolation)

## Idea
Suppose that during your python program you wanted to insert a string in the middle of another string

"One day Mark went to the store"

This operation is known as "string interpolation" or just "interpolation"

---

# String Manipulation (Interpolation)

## Idea
Suppose that during your python program you wanted to insert a string in the middle of another string

"One day Mark went to the store"

This operation is known as "string interpolation" or just "interpolation"

## How it's done
In python this is accomplished through the `.format` function.

---

# String Manipulation (Interpolation)

## Idea
Suppose that during your python program you wanted to insert a string in the middle of another string

"One day Mark went to the store"

This operation is known as "string interpolation" or just "interpolation"

## How it's done
In python this is accomplished through the `.format` function.

```python
print "One day {} went to the store".format("Mark")
```
```
    One day Mark went to the store
```

---

# String Manipulation (Interpolation)

## Idea
Suppose that during your python program you wanted to insert a string in the middle of another string

"One day Mark went to the store"

This operation is known as "string interpolation" or just "interpolation"

## How it's done
In python this is accomplished through the `.format` function.

```python
print "One day {} went to the store".format("Mark")
```
```
    One day Mark went to the store
```
you can also use multiple arguments
```python
print "{} is {}'s favorite day to {}".format("Saturday", "John", "sleep")
```
```
    Saturday is John's favorite day to sleep
```

---

# String Manipulation (Interpolation)

## Idea
Suppose that during your python program you wanted to insert a string in the middle of another string

"One day Mark went to the store"

This operation is known as "string interpolation" or just "interpolation"

## How it's done
In python this is accomplished through the `.format` function.

---

# String Manipulation (Interpolation)

## Idea
Suppose that during your python program you wanted to insert a string in the middle of another string

"One day Mark went to the store"

This operation is known as "string interpolation" or just "interpolation"

## How it's done
In python this is accomplished through the `.format` function.

You can also reuse arguments
```python
print "The r{0} in sp{0} falls {1} in the pl{0}s".format("ain", "mostly")
```
```
    The rain in spain falls mostly in the plains
```

---

# String Manipulation (aside)

## Methods
What's with the weird `"string".format` notation?

Whenver you see `variable.something` python in invoking the "method" called "something" on "variable"

A method is just a function that's bound to an object. We'll talk about objects more later but for now I'll just say that a string is a type of object

---

# String Manipulation (Concatenation)

## Idea
Suppose that during your python program you wanted to combine two strings

---

# String Manipulation (Concatenation)

## Idea
Suppose that during your python program you wanted to combine two strings

You could use the method we _just_ talked about but there's a simpler way

---

# String Manipulation (Concatenation)

## Idea
Suppose that during your python program you wanted to combine two strings

You could use the method we _just_ talked about but there's a simpler way

## How's it done
```python
print "That was " + "easy"
```
```
    That was easy 
```

This is known as "string concatenation" or just "concatention" in programmer parlance

---

# String Manipulation (Length)

## Idea
What about finding the length of a string?

## How's it done
```python
print len("How many letters do I have")
```
```
    26    
```

---

# String Manipulation (Length)

## Idea
What about finding the length of a string?

## How's it done
```python
print len("How many letters do I have")
```
```
    26    
```

Why is `len` not a method?

---

# String Manipulation (Length)

## Idea
What about finding the length of a string?

## How's it done
```python
print len("How many letters do I have")
```
```
    26    
```

Why is `len` not a method?

In short because it's used for other things (that aren't strings). We'll get to that later

---

# String Manipulation (Others)

There are a **lot** of other cool string methods

```python
str.capitalize()
str.center(width[, fillchar])
str.count(sub[, start[, end]])
str.decode([encoding[, errors]])
str.encode([encoding[, errors]])
str.endswith(suffix[, start[, end]])
str.expandtabs([tabsize])¶
str.find(sub[, start[, end]])
str.index(sub[, start[, end]])
str.isalnum()
str.isalpha()
str.isdigit()
str.islower()
str.isspace()
str.istitle() (seriously?)
str.isupper()
str.replace(old, new[, count])
...
```

but I'm not going to go into detail on all of them

---

# Lists (Syntax)

## Idea
A list is just an ordered collection of things

---

# Lists (Syntax)

## Idea
A list is just an ordered collection of things.

## How's it done
```python
groceries = ["Eggs", "Oatmeal", "An entire cow", "A meat cleaver"]
print groceries
```
```
    ['Eggs', 'Oatmeal', 'An entire cow', 'A meat cleaver'] 
```

---

# Lists (Access)

## Idea
In order to access a specific "element" of a list you use the `[index]` notation

---

# Lists (Access)

## Idea
In order to access a specific "element" of a list you use the `[index]` notation

## How's it done
```python
groceries = ["Eggs", "Oatmeal", "An entire cow", "A meat cleaver"]
print groceries[0]
```
```
    Eggs
```

Here we would say that "Eggs" is element at index `0`

---

# Lists (Access)

## Idea
In order to access a specific "element" of a list you use the `[index]` notation

## How's it done
```python
groceries = ["Eggs", "Oatmeal", "An entire cow", "A meat cleaver"]
print groceries[0]
```
```
    Eggs
```

Here we would say that "Eggs" is element at index `0`

### Why do the indices start at `0`?

---

# Lists (Access)

## Idea
In order to access a specific "element" of a list you use the `[index]` notation

## How's it done
```python
groceries = ["Eggs", "Oatmeal", "An entire cow", "A meat cleaver"]
print groceries[0]
```
```
    Eggs
```

Here we would say that "Eggs" is element at index `0`

### Why do the indicies start at `0`?

C/C++ do it this way

Relationship to memory alignment

Dijkstra and half open intervals

etc.

---

# Lists (Access)

## Idea
In order to access a specific "element" of a list you use the `[index]` notation

## How's it done (cont.)
```python
groceries = ["Eggs", "Oatmeal", "An entire cow", "A meat cleaver"]
print "Don't forget to buy {} and {}".format(groceries[0], groceries[2])
```
```
    Don't forget to buy Eggs and An entire cow
```

---

# List Access (Slicing)

## Idea

What if you only need a certain subsection of list?

---

# List Access (Slicing)

## Idea

What if you only need a certain subsection of list?

## How's it done

The notation is basically `[start:end]`
```python
words = ["My", "name", "is", "Judge"]
print words[0:2]
```
```
    ['My', 'name'] 
```

---

# List Access (Slicing)

## Idea

What if you only need a certain subsection of list?

## How's it done

The notation is basically `[start:end]`
```python
words = ["My", "name", "is", "Judge"]
print words[0:2]
```
```
    ['My', 'name'] 
```
`start` or `end` can be omitted and the selection will continue to the beginning or the end of the array (respectively)
```python
words = ["My", "name", "is", "Judge"]
print words[1:]
```
```
    ['name', 'is', 'Judge'] 
```

---

# List Access (Slicing)

## Idea

What if you only need a certain subsection of list?

## How's it done

---

# List Access (Slicing)

## Idea

What if you only need a certain subsection of list?

## How's it done

```python
words = ["My", "name", "is", "Judge"]
print words[:]
```
```
    ['My', 'name', 'is', 'Judge'] 
```

---

# List Manipulation (Insertion)

## Idea

What if you need to add something to a list

---

# List Manipulation (Insertion)

## Idea

What if you need to add something to a list

## How's it done

---

# List Manipulation (Insertion)

## Idea

What if you need to add something to a list

## How's it done

You can add an item to the end of a list using `append`
```python
groceries = ["Eggs", "Oatmeal", "An entire cow", "A meat cleaver"]
groceries.append("seasoning")
print groceries
```
```
    ['Eggs', 'Oatmeal', 'An entire cow', 'A meat cleaver', 'seasoning'] 
```
You can add an item to an arbitrary position by using `insert`
```python
groceries = ["Eggs", "Oatmeal", "An entire cow", "A meat cleaver"]
groceries.insert(2, "A bigger car")
print groceries
```
```
    ['Eggs', 'Oatmeal', 'A bigger car', 'An entire cow', 'A meat cleaver'] 
```

---

# List Manipulation (Removal)

## Idea

What if you need to remove something from a list

---

# List Manipulation (Removal)

## Idea

What if you need to remove something from a list

## How's it done

To remove the element at the back of a list you can use `pop`

```python
groceries = ["Eggs", "Oatmeal", "An entire cow", "A meat cleaver"]
groceries.pop()
print groceries
```
```
    ['Eggs', 'Oatmeal', 'An entire cow']
```

---

# List Manipulation (Removal)

## Idea

What if you need to remove something from a list

## How's it done

To remove the element at the back of a list you can use `pop`

```python
groceries = ["Eggs", "Oatmeal", "An entire cow", "A meat cleaver"]
groceries.pop()
print groceries
```
```
    ['Eggs', 'Oatmeal', 'An entire cow']
```

`pop` actually returns the element that was just removed which you can save for later like so
```python
groceries = ["Eggs", "Oatmeal", "An entire cow", "A meat cleaver"]
last_item = groceries.pop()
print "On second thought let's not get {}".format(last_item)
```
```
    On second thought let's not get A meat cleaver 
```

---

# List Manipulation (Removal)

## Idea

What if you need to remove something from a list

## How's it done

To remove the element at the back of a list you can use `pop`

```python
groceries = ["Eggs", "Oatmeal", "An entire cow", "A meat cleaver"]
groceries.pop()
print groceries
```
```
    ['Eggs', 'Oatmeal', 'An entire cow']
```

If you need to remove the first element with a specific value you can use `remove`
```python
groceries = ["Eggs", "Oatmeal", "An entire cow", "A meat cleaver"]
groceries.remove("An entire cow")
print groceries
```
```
    ['Eggs', 'Oatmeal', 'A meat cleaver']
```

---

# List Manipulation (Removal)

## Idea

What if you need to remove something from a list

## How's it done

To remove the element at the back of a list you can use `pop`

```python
groceries = ["Eggs", "Oatmeal", "An entire cow", "A meat cleaver"]
groceries.pop()
print groceries
```
```
    ['Eggs', 'Oatmeal', 'An entire cow']
```

---

# List Operations (Index)

## Idea

What if you need to find which "index" corrosponds to a given "element"

---

# List Operations (Index)

## Idea

What if you need to find which "index" corrosponds to a given "element"

---

# List Operations (Index)

## Idea

What if you need to find which "index" corrosponds to a given "element"

## How's it done
```python
characters = ["Fred", "Steve", "Sally", "Bob", "Willma", "Tracey", "Waldo", "Dino"]
where_is_waldo = characters.index("Waldo")
print "Waldo is at index {}".format(where_is_waldo)
```
```
 Waldo is at index 6
```
You have to be careful to not look for things that aren't there though
```python
characters = ["Fred", "Steve", "Sally", "Bob", "Willma", "Tracey", "Waldo", "Dino"]
characters.index("that guy")
```
```
 Traceback (most recent call last): 
 File "<stdin>", line 2, in <module> 
 ValueError: 'that guy' is not in list 
```

---

# List Operations (Length)

Remember how I said that `len` could be used on other non-string things?

---

# List Operations (Length)

Remember how I said that `len` could be used on other non-string things?

```python
print len(['a', 'short', 'list', 'of', 'words'])
```
```
    5
```

---

# List Operations (Other)

There are only a few other list methods that we won't touch on (but hopefully they're pretty obvious)
```
list.sort() (sorts a list alphabetically)
list.reverse() (reverses a list)
list.count(x) (counts the number of times x appears in the list)
```

---

# Lists Meet Strings

There are a couple of cool list-string interactions.

---

# Lists Meet Strings

There are a couple of cool list-string interactions.

## Join
### Idea
Let's say you wanted to join a list of words by some seperators like a `...` into one string

---

# Lists Meet Strings

There are a couple of cool list-string interactions.

## Join
### Idea
Let's say you wanted to join a list of words by some seperators like a `...` into one string

### How's it done
```python
print "... ".join(["One", "Two", "Three"])
```
```
    One... Two... Three
```

---

# Lists Meet Strings

There are a couple of cool list-string interactions.

## Join
### Idea
Let's say you wanted to join a list of words by some seperators like a `...` into one string

### How's it done
```python
print "... ".join(["One", "Two", "Three"])
```
```
    One... Two... Three
```
Here we pass a list (note the `[]`) as an "argument" to `join`

---

# Lists Meet Strings

There are a couple of cool list-string interactions.

## Join
### Idea
Let's say you wanted to join a list of words by some seperators like a `...` into one string

### How's it done
```python
print "... ".join(["One", "Two", "Three"])
```
```
    One... Two... Three
```
Here we pass a list (note the `[]`) as an "argument" to `join`

## Going the other way (Split)

### How's it done
```python
print "One... Two... Three".split("... ")
```
```
    ['One', 'Two', 'Three'] 
```

---

# Lists Meet Strings

There are a couple of cool list-string interactions.

## ...wait

You may have already noticed how that this works
---

# Lists Meet Strings

There are a couple of cool list-string interactions.

## ...wait

You may have already noticed how that this works
```python
name = "Admiral Turtle"
print name[8:]
```
```
    Turtle
```

---

# Lists Meet Strings

There are a couple of cool list-string interactions.

## ...wait

You may have already noticed how that this works
```python
name = "Admiral Turtle"
print name[8:]
```
```
    Turtle
```
you can actually access elements of a string just like you can with a list!

---

# Practice

## We're going to make a MadLib generator!

Dear Relative, 
I am having a(n) Adjective time at camp. The counselour is Adjective and the food is Adjective. I 
met Name of person in room and we became Adjective friends. Unfortunately, is Adjective and I Verb ending in "ED" my Body Part so
we couldn`t go Verb ending in "ING" like everybody else. I need more Noun (Plural) and a Noun sharpener, so 
please Adverb Verb more when you Verb back. 
Your Relative, 
Person in room

Make a function which takes a MadLib `string` and a `list` of words to substitute into the MadLib
then prints out the result

## Advanced Version

Prompt a user for each of the blanks and build the list. Print out the result at the end

---

# Practice

## We're going to make a MadLib generator!

Dear Relative, 
I am having a(n) Adjective 
time at camp. The counselour is 
Adjective and the food is 
Adjective. I met 
Name of person in room and we 
became Adjective friends. 
Unfortunately, is Adjective and 
I Verb ending in "ED" my 
Body Part so we couldn`t go 
Verb ending in "ING" like 
everybody else. I need more 
Noun (Plural) and a 
Noun sharpener, so please 
Adverb 
Verb more when you 
Verb back. 
Your Relative, 
Person in room

Make a function which takes a MadLib `string` and a `list` of words to 
substitute into the MadLib
then prints out the result

## Advanced Version

Prompt a user for each of the blanks and build the list. Print out the result 
at the end
## Also this
<img style="width: 50%; height: 50%; left: 120px; top: -60px; position: relative" src="http://www.distractify.netdna-cdn.com/wp-content/uploads//2014/01//the-best-boops-of-all-time-this-is-my-new-favorite-thing-lol-7.gif"></img>

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