X-Git-Url: https://git.njae.me.uk/?a=blobdiff_plain;f=slides%2Fcaesar-encipher.html;h=4afd78dad4f3367c5107a99d0f40ff8f1e0aa037;hb=7203ac94911556e2b4bf4caab6f5285445faed3b;hp=1cdf8ddf0ad3cc22da75e10f27385c2f569ce118;hpb=2c871791002cd822e2e6d8a81c9728049d66c2c1;p=cipher-training.git
diff --git a/slides/caesar-encipher.html b/slides/caesar-encipher.html
index 1cdf8dd..4afd78d 100644
--- a/slides/caesar-encipher.html
+++ b/slides/caesar-encipher.html
@@ -1,7 +1,7 @@
- Title
+ Caesar cipher
@@ -35,7 +51,62 @@
-* Letter-by-letter enciphering
+Letter-by-letter enciphering
+
+---
+
+layout: true
+
+.indexlink[[Index](index.html)]
+
+---
+
+# Enciphering and deciphering
+
+## Arithmetic on letters
+
+Convert .plaintext[letter] â .plaintext[number] â
+.ciphertext[number] â .ciphertext[letter]
+
+Functions you will need
+
+```python
+ord()
+
+chr()
+
+%
+```
+
+* 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
---
@@ -43,6 +114,7 @@
```python
import string
+
string.ascii_letters
string.ascii_lowercase
string.ascii_uppercase
@@ -52,11 +124,30 @@ string.punctuation
---
+# DRY and YAGNI
+
+Is your code DRY?
+
+---
+
# Doctest
* Why document?
* Why test?
+```python
+def caesar_encipher_letter(letter, shift):
+ """Encipher a letter, given a shift amount
+
+ >>> caesar_encipher_letter('a', 1)
+ 'b'
+ """
+ if letter in string.ascii_letters:
+ .
+ .
+ .
+```
+
---
# The magic doctest incantation
@@ -69,7 +160,18 @@ if __name__ == "__main__":
---
-# Doing all the letters
+# Doing the whole message
+
+## Test-first developement
+
+1. Write the tests.
+ * They will fail. There is no code.
+2. Write code until the tests pass.
+3. Refactor.
+
+---
+
+# Doing the whole message
## Abysmal
@@ -79,11 +181,13 @@ for i in range(len(plaintext)):
ciphertext += caesar_encipher_letter(plaintext[i], key)
```
+Try it in IPython
+
---
-# Doing all the letters
+# Doing the whole message
-## (Merely) Bad
+## Bad
```python
ciphertext = ''
@@ -91,34 +195,40 @@ for p in plaintext:
ciphertext += caesar_encipher_letter(p, key)
```
+...but easily generalisable
+
---
-# Doing all the letters
+# Doing the whole message
## Good (but unPythonic)
```python
-ciphertext = map(lambda p: caesar_encipher_letter(p, key),
- plaintext)
+ciphertext = map(lambda p: caesar_encipher_letter(p, key), plaintext)
```
---
-# Doing all the letters
+# Doing the whole message
## Best
```python
-ciphertext = [caesar_encipher_letter(p, key)
- for p in plaintext]
+ciphertext = [caesar_encipher_letter(p, key) for p in plaintext]
```
+---
+# Not all iterables are equal
+
+```python
+''.join()
+```
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