Announcements

• Scheme Project Phase 1 due today
• Phases 2 and 3 due Friday
• Final project due on Tuesday
• Would recommend getting the whole project done by the weekend
• I'm ending today's discussion slightly earlier so I can go to Dwinelle!
  • come with me pls thx

Notes from last section

• Avid 3b1b watcher?
  • yep
  • got me through linalg/calc
• your explanation of tail calls/recursion was so good!! made me understand the lecture so much better
  • honestly a shocker because i thought i crapped the bed
• Python >> Scheme
  • i strongly agree

Notes from last section

• What notes app do you use on your ipad?
  • Goodnotes
  • Used to use OneNote/Microsoft Journal back when I used a surface/windows though
• In the game Pokemon, there is a tactic known as Fear. this is an acronym, standing for Focus sash, Endeavor, (quick) Attack, and Rattata. [...]
  • I personally liked the shell bell/aron/sandstorm thing a lot more just cause I thought it was funnier and could potentially last longer
  • There was also a FEAR reference in the Fall 2022 Final
  • fun question

Temperature Check

• RegEx

RegEx

• Regular Expressions are used to describe sets of strings that meet certain criteria
• Very useful for pattern matching (will see examples later)
  • Used in real life all the time!
  • Can be used for super simple patterns (egg in text)
  • Can also be very complicated (validating passwords)
• regex101.com
  • Super useful for learning/debugging your regular expressions, but don't rely on this!
  • (You won't have this resource for the exam! Don't use it as a GPS)

Character Classes

• If you want to search for a certain character in a set of characters, use character classes
• Can use pre-defined classes, or specify your own

Specified:

Character Classes

Predefined character classes

Combining Multiple Patterns

• If you put a pattern after another pattern, you can have a regular expression that matches both of those characters in succession
  • AB - Matches A, then B (both are required)
  • A[xt]e Matches A, then either x or t, then E
    • Axe or Ate are the things that get matched
• | is the separator used to match 'or'
  • A|B - Matches either A or B

Quantifiers

Groups

• Parentheses are used to group certain patterns together
  • Useful with quantifiers
  • (Ha)+ and Ha+ do different things!

Anchors

Special Characters

Some characters cannot be written directly because they have special roles in RegEx

• \[](){}+*?|$^.
• Inside a character class, you need to escape -
• To escape these characters, you need to put a backslash before them
  • The quick brown fox jumped over the lazy dog\.

RegEx in Python

• For Python, we use r-strings to write regex patterns
• With r-strings in Python, backslashes are treated specially in some cases (for example with \n, or \t). What r-strings do in this case is that they automatically escape the backslashes for these special characters, so they look like real backslashes rather than what Python designates for those characters.
• r"<insert string here>" - the r at the front makes a string an r-string
  • Python also has f-strings which are pretty useful/interesting

Mental Health Resources

• CAPS:
  • If you need to talk to a professional, please call CAPS at 510-642-9494.
• After Hours Assistance
  • For any assistance after hours, details on what to do can be found at this link