You look at it till

a solution occurs

Brandon Rhodes

@brandon_rhodes

PyCon IE
Dublin, Ireland
2017 October 21

Patterns are everywhere

McIlroy

tr -cs A-Za-z '\n' |
tr A-Z a-z |
sort |
uniq -c |
sort -rn |
sed ${1}q

Pipes!

Clipboard?

Clipboard transforms

Links
Equations
Markdown

Pattern ↔ Search

Search

Example: sending a string

How does the receiver know when

the whole string has arrived?

──┬─> close the channel

DCD
HTTP/0.9 server close()
shutdown(s, SHUT_WR)
End of file

──┬─> close the channel
  │
  └────┬─> fixed length

int
float
text?
RPC

──┬── close the channel
  │
  └────┬── fixed length
       │
       │
       ├── delimit ──┤

──┬── close the channel
  │
  └────┬── fixed length
       │
       │            (<)──── literal
       ├── delimit ──┤

HTTP Header

Content-Type: text/html␍␊

──┬── close the channel
  │
  └────┬── fixed length
       │
       │            (<)──── literal
       ├── delimit ──┤

ASCII: ␍, ␊, TAB, but also offers

SOH, STX, ETX, EOT, EM, FS, GS, RS, US

──┬── close the channel
  │
  └────┬── fixed length
       │
       │            (<)──── literal
       ├── delimit ──┤

"You have $count ${noun}s"

→ “You have 5 apples”

“But what if the gym is on fire?”

──┬── close the channel
  │
  └────┬── fixed length
       │
       │            (<)──── literal
       ├── delimit ──┤
                    (≥)─┬── encode

>> b64encode('Null \0 SOH \001 DEL \177')
'TnVsbCAAIFNPSCABIERFTCB/'

──┬── close the channel
  │
  └────┬── fixed length
       │
       │            (<)──── literal
       ├── delimit ──┤
                    (≥)─┬── encode
                        │
                        └── escape

In SQL: 'I Won''t Back Down'

Python: 'I Won\'t Back Down'

──┬── close the channel
  │
  └────┬── fixed length
       │
       │            (<)──── literal
       ├── delimit ──┤
       │            (≥)─┬── encode
       │                │
       │                └── escape
       │
       └── length prefix

FORTRAN 66 — 100 FORMAT (11HHELLO WORLD)

But…

How many bytes does it

take to express a length?

──┬── close the channel
  │
  └────┬── fixed length
    ^  │
    │  │            (<)──── literal
    │  ├── delimit ──┤
    │  │            (≥)─┬── encode
    │  │                │
    │  │                └── escape
    │  │
    │  └── length prefix  ─┐
    │                      │
    └──────────────────────┘

HTTP/1.1 200 OK␍␊
Content-Type: text/html; charset=UTF-8␍␊
Content-Encoding: UTF-8␍␊
Content-Length: 39␍␊
␍␊
<html><body>Hello, world!</body></html>

──┬──
  │
  └────┬──
       │
       │    ┌─────
       ├────┤
       │    └──┬──
       │       │
       │       └──
       └──

Pattern ↔ Search

General Physics I — Dr. Wiesenfeld

Applied Combinatorics
Understanding & Constructing Proofs
Calculus IV
Calculus V

Derivative ≪ Integral ≪ Differential Equations

George Pólya

“In order to solve this
differential equation you look at it

George Pólya

“In order to solve this
differential equation you look at it
till a solution occurs to you.”

Pattern ↔ Search ↔ ?

Zen and the Art

of Motorcycle Maintenance

Robert M. Pirsig

Pattern ↔ Search ↔ Stuck

Claim

Novices generate programs

by Pattern and Search

Claim

Novices generate programs

by Pattern and Search

but once something goes wrong

they start debugging from

a default state of Stuck

Why?

Because anything could

have gone wrong —

nothing constrains the error to be in

a part of the system they understand!

Example: getting sidetracked by

a problem outside the code itself

You saved to the wrong file
… in the wrong copy of the repository
… on the wrong computer
You need to restart the program
You are reloading the wrong URL
The traceback names a different line of code
Your module name is the same as a stdlib module

scientific method

“The real purpose of
the scientific method
is to make sure nature hasn’t
misled you into thinking you know
something you actually don’t know.”

— Robert Pirsig

Novices get stuck

Corollary:

The default emotions of computer

programming are hope and misery

“Test-driven development is a way of

managing fear during programming.”

— Kent Beck,

Test Driven Development By Example

How can we support novice programmers?

Encourage writing one line at a time
Version control + frequent commits
Encourage them to call for backup!
Let them write things twice

Fred Brooks

“plan to throw one away;

you will, anyhow”

Fred Brooks

“plan to throw one away;

you will, anyhow”

(but not always the first!)

DjangoCon 2014:

Once my code
is finally working
it is probably better
described as barely working

Once new code works,
I am probably about
halfway done

“Even fairly good students,
when they have obtained the solution of the
problem and written down neatly the argument,
shut their books and look for something else.

Doing so, they miss an important

and instructive phase of the work.”

— George Pólya, How to Solve It

Encourage novice programmers to

explore past their first solution

Why?

Search is the programmer’s

defense against stuck

“Your problem may be modest,
but if it challenges your curiosity
and brings into play your inventive faculties,
and if you solve it by your own means,
you may experience the tension and
enjoy the triumph of discovery.”

— George Pólya, How to Solve It

Pattern ↔ Search ↔ Stuck

Thank you!

@brandon_rhodes