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 @@ <!DOCTYPE html> <html> <head> - <title>Title</title> + <title>Caesar cipher</title> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/> <style type="text/css"> /* Slideshow styles */ @@ -12,11 +12,10 @@ font-weight: 400; margin-bottom: 0; } - h1 { font-size: 4em; } + h1 { font-size: 3em; } h2 { font-size: 2em; } h3 { font-size: 1.6em; } a, a > code { - /* color: rgb(249, 38, 114); */ text-decoration: none; } code { @@ -26,6 +25,23 @@ border-radius: 5px; font-size: 16px; } + .plaintext { + background: #272822; + color: #80ff80; + text-shadow: 0 0 20px #333; + padding: 2px 5px; + } + .ciphertext { + background: #272822; + color: #ff6666; + text-shadow: 0 0 20px #333; + padding: 2px 5px; + } + .indexlink { + position: absolute; + bottom: 1em; + left: 1em; + } </style> </head> <body> @@ -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() +``` </textarea> <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> </body> </html> \ No newline at end of file