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- <title>Title</title>
+ <title>Caesar cipher</title>
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+ h1 { font-size: 3em; }
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---
+layout: true
+
+.indexlink[[Index](index.html)]
+
+---
+
# Enciphering and deciphering
## Arithmetic on letters
chr()
-mod()
+%
```
* What are good test cases?
---
+# Using the tools
+
+Before doing anything, create a new branch in Git
+
+* This will keep your changes isolated
+
+Experiment in IPython (ephemeral, for us)
+
+Once you've got something working, copy the code into a `.py` file (permanent and reusable)
+
+```python
+from imp import reload
+
+import test
+reload(test)
+from test import *
+```
+
+Re-evaluate the second cell to reload the file into the IPython notebook
+
+When you've made progress, make a Git commit
+
+* Commit early and often!
+
+When you've finished, change back to `master` branch and `merge` the development branch
+
+---
+
# The [string module](http://docs.python.org/3.3/library/string.html) is your friend
```python
```
---
+
# DRY and YAGNI
Is your code DRY?
'b'
"""
if letter in string.ascii_letters:
+ .
+ .
+ .
```
---
-# My tests
-
-```python
-def caesar_encipher_letter(letter, shift):
- """Encipher a letter, given a shift amount
-
- >>> caesar_encipher_letter('a', 1)
- 'b'
- >>> caesar_encipher_letter('a', 2)
- 'c'
- >>> caesar_encipher_letter('b', 2)
- 'd'
- >>> caesar_encipher_letter('x', 2)
- 'z'
- >>> caesar_encipher_letter('y', 2)
- 'a'
- >>> caesar_encipher_letter('z', 2)
- 'b'
- >>> caesar_encipher_letter('z', -1)
- 'y'
- >>> caesar_encipher_letter('a', -1)
- 'z'
- """
- if letter in string.ascii_letters:
-```
----
-
# The magic doctest incantation
```python
---
-# Doing all the letters
+# Doing the whole message
## Test-first developement
---
-# Doing all the letters
+# Doing the whole message
## Abysmal
ciphertext += caesar_encipher_letter(plaintext[i], key)
```
+Try it in IPython
+
---
-# Doing all the letters
+# Doing the whole message
## Bad
ciphertext += caesar_encipher_letter(p, key)
```
+...but easily generalisable
+
---
-# Doing all the letters
+# Doing the whole message
## Good (but unPythonic)
---
-# Doing all the letters
+# Doing the whole message
## Best
<script src="http://gnab.github.io/remark/downloads/remark-0.6.0.min.js" type="text/javascript">
</script>
<script type="text/javascript">
- var slideshow = remark.create();
+ var slideshow = remark.create({ ratio: "16:9" });
</script>
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