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# Engineering 1020: Introduction to Programming

.title[
  .lecture[Lecture 8:]
  .title[Iteration and strings]
  
  
]

.footer[[/lecture/8/](/lecture/8/)]

---

# Designing with loops

### Work from the _inside out:_

1. What should this loop do **every time**?
--

2. How do we start and finish?

### Example: summation

???

Example:

1. Ask a user to enter some numbers.
2. Add them up until the user enters an empty string.
3. Print the total.

### [Project Euler](https://projecteuler.net)

???

After today's lecture, you will be equipped to tackle
[problem 16 in Project Euler](https://projecteuler.net/problem=16).
It's a puzzle, so expect to spend some time thinking about different
ways to tackle it, but you will have everything you need to know
in order to do it!

And remember: don't think like a _mathemetician_, think like a
_programmer_.

---

# Iteration

### Walking through a bunch of things, _one at a time_

### IRL: design _iterations_

### Computing: loops!

.floatright[
```python
for letter in 'Jonathan Anderson':
	print(letter)
```
]

* get "next" letter, use it
--

* ... until no more letters

#### Later: lists, arrays and `iter()`

---

# Iteration problems

1. Count frequency of "e" in a string (upper- and lower-case)
--

2. For each letter in a string, count instances of that letter
--

3. Count upper-case characters in a string
--
 **(??)**

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# More string detail

### What is a string?

### What is a character?

## A, B, C
--
... 🧙?

### Some history:
--
 [ASCII](https://en.wikipedia.org/wiki/ASCII#Character_set)
???

How do you represent language to others?

* sounds

* writing

How would you transmit letters over a distance?

https://en.wikipedia.org/wiki/Telegraph_code#Electrical_telegraph_codes

--
 and [Unicode](https://en.wikipedia.org/wiki/Unicode)

### Python: `chr()` and `ord()`

---

# Iteration problems

1. Count frequency of "e" in a string (upper- and lower-case)
2. For each letter in a string, count instances of that letter
3. **Count upper-case characters in a string**
--

4. Does a string have more upper- or lower-case characters?
5. Add up a string's letter values (A=1, B=2, etc.)
6. Compare two strings by alphabetical order

---
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(here endeth the lesson)