class: big, middle

# Engineering 1020: Introduction to Programming

.title[
  .lecture[Lecture 14:]
  .title[Local variables]
  
  
]

.footer[[/lecture/14/](/lecture/14/)]

---

# Last time:

### Function semantics

### Function syntax

### Function parameters and arguments

---

# Today

### Scope

### Global variables

### Keyword arguments

### Default arguments

---

# Recall: arguments and parameters

### Arguments: _values_ passed into functions

```python
f(1, 2+2, x*3)
```

### Parameters: _variables_ initialized by arguments

```python
def f(x, y, z):
    return x + y * z
```

---

# Variable scope

### Within a function:

```python
def foo(x, y):
    z = x % y

return z
```

These variables are _local_ to the function
--
  
 (i.e., separate from other variables defined in the file)

---

# More variable scope

### Example of separate variables:

```python
name = "Jon"

def foo():
    name = "foo"

print("name:", name)

foo()
```

Two `name` variables:
--
  **separate memory**
--
 and **separate values**

---

# Global variables

### What does this script do?

```python
x = 12

def foo():
    x = 13

foo()
print(x)
```

---

# Global variables

### To access a global variable:

```python
x = 12

def foo():
    global x
    x = 13

foo()
print(x)
```

---

# Keyword arguments

### Using the colour LCD screen:

```python
rgb_lcd_colour(255, 0, 255)
```

(aside: what colour is this?)

### Easier to tell now:

```python
rgb_lcd_colour(red=255, green=0, blue=255)
```

No _positional_ arguments after the first _keyword_ argument

---

# Default arguments

.floatright[
```python
def get_user_input(prompt='Input? '):
    return input(prompt)
```
]

Passed to the parameter if no argument in the call

#### One way to print:

```python
print('these', 'words', 'go', 'on', 'one', 'line')
print('these', 'words', 'go', 'on', 'the', 'next', 'line')
```

#### Another way:

```python
print(1, 2, 3, sep='*', end=' + ')
print(4, 5, 6, sep='*')
```

---

# Summary

### Scope

### Global variables

### Keyword arguments

### Default arguments

---
class: big, middle

(here endeth the lesson)