introduction (week 1)

Transcription

1 introduction (week 1) Matt Valeriote 7 January, 2019

2 Introduction Administrative trivia

3 Introduction Administrative trivia Instructor: Matt Valeriote

4 Introduction Administrative trivia Instructor: Matt Valeriote please include 1mp3 in Subject:

5 Introduction Administrative trivia Instructor: Matt Valeriote please include 1mp3 in Subject:

6 Introduction Administrative trivia Instructor: Matt Valeriote please include 1mp3 in Subject: HH 323; office and by appointment

7 Introduction Administrative trivia Instructor: Matt Valeriote please include 1mp3 in Subject: HH 323; office and by appointment TAs: Aghigh Farhadichesmehmorvari and Nik Pocuca

8 Introduction Administrative trivia Instructor: Matt Valeriote please include 1mp3 in Subject: HH 323; office and by appointment TAs: Aghigh Farhadichesmehmorvari and Nik Pocuca Grading:

9 Introduction Administrative trivia Instructor: Matt Valeriote please include 1mp3 in Subject: HH 323; office and by appointment TAs: Aghigh Farhadichesmehmorvari and Nik Pocuca Grading: midterms (two of them) 20% each

10 Introduction Administrative trivia Instructor: Matt Valeriote please include 1mp3 in Subject: HH 323; office and by appointment TAs: Aghigh Farhadichesmehmorvari and Nik Pocuca Grading: midterms (two of them) 20% each final 40%

11 Introduction Administrative trivia Instructor: Matt Valeriote please include 1mp3 in Subject: HH 323; office and by appointment TAs: Aghigh Farhadichesmehmorvari and Nik Pocuca Grading: midterms (two of them) 20% each final 40% quizzes 5%

12 Introduction Administrative trivia Instructor: Matt Valeriote please include 1mp3 in Subject: HH 323; office and by appointment TAs: Aghigh Farhadichesmehmorvari and Nik Pocuca Grading: midterms (two of them) 20% each final 40% quizzes 5% assignments 10%

13 Introduction Administrative trivia Instructor: Matt Valeriote please include 1mp3 in Subject: HH 323; office and by appointment TAs: Aghigh Farhadichesmehmorvari and Nik Pocuca Grading: midterms (two of them) 20% each final 40% quizzes 5% assignments 10% project 5%

14 Laptop policy

15 Laptop policy Course webpage: and Avenue

16 Laptop policy Course webpage: and Avenue Expectations of professor and students

17 Laptop policy Course webpage: and Avenue Expectations of professor and students Textbook (optional): Gries et al. Practical Programming 2d ed., available from the bookstore, the publisher (The Pragmatic Bookshelf), or amazon.ca

18 Laptop policy Course webpage: and Avenue Expectations of professor and students Textbook (optional): Gries et al. Practical Programming 2d ed., available from the bookstore, the publisher (The Pragmatic Bookshelf), or amazon.ca also see resources

19 Laptop policy Course webpage: and Avenue Expectations of professor and students Textbook (optional): Gries et al. Practical Programming 2d ed., available from the bookstore, the publisher (The Pragmatic Bookshelf), or amazon.ca also see resources Course content: reasonable balance among

20 Laptop policy Course webpage: and Avenue Expectations of professor and students Textbook (optional): Gries et al. Practical Programming 2d ed., available from the bookstore, the publisher (The Pragmatic Bookshelf), or amazon.ca also see resources Course content: reasonable balance among nitty-gritty practical programming instruction:

21 Laptop policy Course webpage: and Avenue Expectations of professor and students Textbook (optional): Gries et al. Practical Programming 2d ed., available from the bookstore, the publisher (The Pragmatic Bookshelf), or amazon.ca also see resources Course content: reasonable balance among nitty-gritty practical programming instruction:... I just sat down in front of a text editor, with nothing but thoughts, and ended up with a program that did exactly what I wanted it to a few hours later... (ankit panda)

22 Laptop policy Course webpage: and Avenue Expectations of professor and students Textbook (optional): Gries et al. Practical Programming 2d ed., available from the bookstore, the publisher (The Pragmatic Bookshelf), or amazon.ca also see resources Course content: reasonable balance among nitty-gritty practical programming instruction:... I just sat down in front of a text editor, with nothing but thoughts, and ended up with a program that did exactly what I wanted it to a few hours later... (ankit panda) conceptual foundations of computing/computer science

23 Laptop policy Course webpage: and Avenue Expectations of professor and students Textbook (optional): Gries et al. Practical Programming 2d ed., available from the bookstore, the publisher (The Pragmatic Bookshelf), or amazon.ca also see resources Course content: reasonable balance among nitty-gritty practical programming instruction:... I just sat down in front of a text editor, with nothing but thoughts, and ended up with a program that did exactly what I wanted it to a few hours later... (ankit panda) conceptual foundations of computing/computer science context/culture of mathematical/scientific computing

24 Laptop policy Course webpage: and Avenue Expectations of professor and students Textbook (optional): Gries et al. Practical Programming 2d ed., available from the bookstore, the publisher (The Pragmatic Bookshelf), or amazon.ca also see resources Course content: reasonable balance among nitty-gritty practical programming instruction:... I just sat down in front of a text editor, with nothing but thoughts, and ended up with a program that did exactly what I wanted it to a few hours later... (ankit panda) conceptual foundations of computing/computer science context/culture of mathematical/scientific computing interesting applications

25 Installing Python

26 Installing Python CodeLab:

27 Installing Python CodeLab: Jupyter:

28 Installing Python CodeLab: Jupyter: PythonAnywhere

29 Installing Python CodeLab: Jupyter: PythonAnywhere Everyone must have access to a computer with Python3 installed.

30 Installing Python CodeLab: Jupyter: PythonAnywhere Everyone must have access to a computer with Python3 installed. See installation instructions

31 More interesting stuff Using computers in math and science

32 More interesting stuff Using computers in math and science math users vs. understanders vs. developers

33 More interesting stuff Using computers in math and science math users vs. understanders vs. developers develop conjectures; draw pictures; write manuscripts

34 More interesting stuff Using computers in math and science math users vs. understanders vs. developers develop conjectures; draw pictures; write manuscripts mathematical proof (e.g. four-colo(u)r theorem and other examples); computer algebra

35 More interesting stuff Using computers in math and science math users vs. understanders vs. developers develop conjectures; draw pictures; write manuscripts mathematical proof (e.g. four-colo(u)r theorem and other examples); computer algebra applied math: cryptography, tomography, logistics, finance, fluid dynamics,...

36 More interesting stuff Using computers in math and science math users vs. understanders vs. developers develop conjectures; draw pictures; write manuscripts mathematical proof (e.g. four-colo(u)r theorem and other examples); computer algebra applied math: cryptography, tomography, logistics, finance, fluid dynamics,... applied statistics: bioinformatics, Big Data/analytics,...

37 Fun! Hello, world (always the first program you write in a new computer language) print('hello, world!') ## hello, world! Python as a fancy calculator: print(62**2*27/5+3) ## reference: Python intro section 3.1.1

38 Interlude: about Python

39 Interlude: about Python programming languages

40 Interlude: about Python programming languages Python: scripting; high-level; glue; general-purpose; flexible

41 Interlude: about Python programming languages Python: scripting; high-level; glue; general-purpose; flexible contrast: domain-specific scripting languages (MATLAB, R, Mathematica, Maple)

42 Interlude: about Python programming languages Python: scripting; high-level; glue; general-purpose; flexible contrast: domain-specific scripting languages (MATLAB, R, Mathematica, Maple) contrast: general-purpose scripting languages (Perl, PHP)

43 Interlude: about Python programming languages Python: scripting; high-level; glue; general-purpose; flexible contrast: domain-specific scripting languages (MATLAB, R, Mathematica, Maple) contrast: general-purpose scripting languages (Perl, PHP) contrast: general-purpose compiled languages (Java, C, C++) ( close to the metal )

44 Interlude: about Python programming languages Python: scripting; high-level; glue; general-purpose; flexible contrast: domain-specific scripting languages (MATLAB, R, Mathematica, Maple) contrast: general-purpose scripting languages (Perl, PHP) contrast: general-purpose compiled languages (Java, C, C++) ( close to the metal ) relatively modern (1990s; Python 3, 2008)

45 Interlude: about Python programming languages Python: scripting; high-level; glue; general-purpose; flexible contrast: domain-specific scripting languages (MATLAB, R, Mathematica, Maple) contrast: general-purpose scripting languages (Perl, PHP) contrast: general-purpose compiled languages (Java, C, C++) ( close to the metal ) relatively modern (1990s; Python 3, 2008) currently the 3rd most popular computer language overall (up from 8th in 2015); most popular for teaching

46 Interlude: about Python programming languages Python: scripting; high-level; glue; general-purpose; flexible contrast: domain-specific scripting languages (MATLAB, R, Mathematica, Maple) contrast: general-purpose scripting languages (Perl, PHP) contrast: general-purpose compiled languages (Java, C, C++) ( close to the metal ) relatively modern (1990s; Python 3, 2008) currently the 3rd most popular computer language overall (up from 8th in 2015); most popular for teaching well suited to mathematical/scientific/technical (NumPy; SciPy; Python in Finance)

47 Interlude: about Python programming languages Python: scripting; high-level; glue; general-purpose; flexible contrast: domain-specific scripting languages (MATLAB, R, Mathematica, Maple) contrast: general-purpose scripting languages (Perl, PHP) contrast: general-purpose compiled languages (Java, C, C++) ( close to the metal ) relatively modern (1990s; Python 3, 2008) currently the 3rd most popular computer language overall (up from 8th in 2015); most popular for teaching well suited to mathematical/scientific/technical (NumPy; SciPy; Python in Finance) ex.: Sage; BioPython

48 the prime walk (from math.stackexchange.ca)

49 the prime walk (from math.stackexchange.ca) 1. start at the origin, heading right, counting up from 1

50 the prime walk (from math.stackexchange.ca) 1. start at the origin, heading right, counting up from 1 2. move forward one space, counting up, until you find a prime

51 the prime walk (from math.stackexchange.ca) 1. start at the origin, heading right, counting up from 1 2. move forward one space, counting up, until you find a prime 3. turn 90 clockwise

52 the prime walk (from math.stackexchange.ca) 1. start at the origin, heading right, counting up from 1 2. move forward one space, counting up, until you find a prime 3. turn 90 clockwise 4. repeat steps 2 and 3 until you get bored

53 the prime walk (from math.stackexchange.ca) 1. start at the origin, heading right, counting up from 1 2. move forward one space, counting up, until you find a prime 3. turn 90 clockwise 4. repeat steps 2 and 3 until you get bored Note:

54 the prime walk (from math.stackexchange.ca) 1. start at the origin, heading right, counting up from 1 2. move forward one space, counting up, until you find a prime 3. turn 90 clockwise 4. repeat steps 2 and 3 until you get bored Note: Here is some python code that implements this procedure: matt/1mp3/primewalk.py

55 the prime walk (from math.stackexchange.ca) 1. start at the origin, heading right, counting up from 1 2. move forward one space, counting up, until you find a prime 3. turn 90 clockwise 4. repeat steps 2 and 3 until you get bored Note: Here is some python code that implements this procedure: matt/1mp3/primewalk.py easier to understand/modify than write from scratch

56 the prime walk (from math.stackexchange.ca) 1. start at the origin, heading right, counting up from 1 2. move forward one space, counting up, until you find a prime 3. turn 90 clockwise 4. repeat steps 2 and 3 until you get bored Note: Here is some python code that implements this procedure: matt/1mp3/primewalk.py easier to understand/modify than write from scratch build on existing components (modules)

57 Interfaces

58 Interfaces command line/console (Spyder: Consoles/Open an IPython Console or Ctrl+T)

59 Interfaces command line/console (Spyder: Consoles/Open an IPython Console or Ctrl+T) programming editor

60 Interfaces command line/console (Spyder: Consoles/Open an IPython Console or Ctrl+T) programming editor integrated development environment (IDE)

61 Interfaces command line/console (Spyder: Consoles/Open an IPython Console or Ctrl+T) programming editor integrated development environment (IDE) not MS Word!

62 Interfaces command line/console (Spyder: Consoles/Open an IPython Console or Ctrl+T) programming editor integrated development environment (IDE) not MS Word! Features

63 Interfaces command line/console (Spyder: Consoles/Open an IPython Console or Ctrl+T) programming editor integrated development environment (IDE) not MS Word! Features syntax highlighting

64 Interfaces command line/console (Spyder: Consoles/Open an IPython Console or Ctrl+T) programming editor integrated development environment (IDE) not MS Word! Features syntax highlighting bracket-matching

65 Interfaces command line/console (Spyder: Consoles/Open an IPython Console or Ctrl+T) programming editor integrated development environment (IDE) not MS Word! Features syntax highlighting bracket-matching integrated help

66 Interfaces command line/console (Spyder: Consoles/Open an IPython Console or Ctrl+T) programming editor integrated development environment (IDE) not MS Word! Features syntax highlighting bracket-matching integrated help integrated debugging tools

67 Interfaces command line/console (Spyder: Consoles/Open an IPython Console or Ctrl+T) programming editor integrated development environment (IDE) not MS Word! Features syntax highlighting bracket-matching integrated help integrated debugging tools integrated project management tools

68 Assignment and types (PP Ch. 2)

69 Assignment and types (PP Ch. 2) superficially simple

70 Assignment and types (PP Ch. 2) superficially simple set aside memory space, create a symbol that points to that space

71 Assignment and types (PP Ch. 2) superficially simple set aside memory space, create a symbol that points to that space = is the assignment operator ( gets, not equals )

72 Assignment and types (PP Ch. 2) superficially simple set aside memory space, create a symbol that points to that space = is the assignment operator ( gets, not equals ) <variable> = <value>

73 Assignment and types (PP Ch. 2) superficially simple set aside memory space, create a symbol that points to that space = is the assignment operator ( gets, not equals ) <variable> = <value> variable names

74 Assignment and types (PP Ch. 2) superficially simple set aside memory space, create a symbol that points to that space = is the assignment operator ( gets, not equals ) <variable> = <value> variable names what is legal? (names include letters, numbers, underscores, must start with a letter or underscore)

75 Assignment and types (PP Ch. 2) superficially simple set aside memory space, create a symbol that points to that space = is the assignment operator ( gets, not equals ) <variable> = <value> variable names what is legal? (names include letters, numbers, underscores, must start with a letter or underscore) what is customary? convention is variables_like_this ( snake case )

76 Assignment and types (PP Ch. 2) superficially simple set aside memory space, create a symbol that points to that space = is the assignment operator ( gets, not equals ) <variable> = <value> variable names what is legal? (names include letters, numbers, underscores, must start with a letter or underscore) what is customary? convention is variables_like_this ( snake case ) what works well? v vs. temporary_variable_for_loop

77 Assignment and types (PP Ch. 2) superficially simple set aside memory space, create a symbol that points to that space = is the assignment operator ( gets, not equals ) <variable> = <value> variable names what is legal? (names include letters, numbers, underscores, must start with a letter or underscore) what is customary? convention is variables_like_this ( snake case ) what works well? v vs. temporary_variable_for_loop same principles apply to file, directory/folder names

78 variables are of different types

79 variables are of different types built-in: integer (int), floating-point (float), complex, Boolean (bool: True or False),

80 variables are of different types built-in: integer (int), floating-point (float), complex, Boolean (bool: True or False), dynamic typing

81 variables are of different types built-in: integer (int), floating-point (float), complex, Boolean (bool: True or False), dynamic typing Python usually does what you mean, converts types when sensible

82 variables are of different types built-in: integer (int), floating-point (float), complex, Boolean (bool: True or False), dynamic typing Python usually does what you mean, converts types when sensible (relatively) strong typing

83 variables are of different types built-in: integer (int), floating-point (float), complex, Boolean (bool: True or False), dynamic typing Python usually does what you mean, converts types when sensible (relatively) strong typing try type(x) for different possibilities (x=3; x=3.0; x="a")

84 variables are of different types built-in: integer (int), floating-point (float), complex, Boolean (bool: True or False), dynamic typing Python usually does what you mean, converts types when sensible (relatively) strong typing try type(x) for different possibilities (x=3; x=3.0; x="a") what happens if you try x=a?

85 variables are of different types built-in: integer (int), floating-point (float), complex, Boolean (bool: True or False), dynamic typing Python usually does what you mean, converts types when sensible (relatively) strong typing try type(x) for different possibilities (x=3; x=3.0; x="a") what happens if you try x=a? don t be afraid to experiment!

86 x=3 y=3.0 z="a" q=complex(1,2) type(x+y) ## mixed arithmetic type(int(x+y)) ## int(), float() convert explicitly type(x+z) type(q) type(x+q) type(true) type(true+1) Try these in a python console or check out the Python tutor for these examples

87 Arithmetic operators, precedence

88 Arithmetic operators, precedence exponentiation (**)

89 Arithmetic operators, precedence exponentiation (**) negation ( unary minus ) (-)

90 Arithmetic operators, precedence exponentiation (**) negation ( unary minus ) (-) multiplication/division (*,/,//=integer division,%=remainder)

91 Arithmetic operators, precedence exponentiation (**) negation ( unary minus ) (-) multiplication/division (*,/,//=integer division,%=remainder) addition/subtraction (+, - ( binary ))

92 Arithmetic operators, precedence exponentiation (**) negation ( unary minus ) (-) multiplication/division (*,/,//=integer division,%=remainder) addition/subtraction (+, - ( binary )) When in doubt, use parentheses! Puzzle: what is -1**2? Why?

93 Arithmetic operators, precedence exponentiation (**) negation ( unary minus ) (-) multiplication/division (*,/,//=integer division,%=remainder) addition/subtraction (+, - ( binary )) When in doubt, use parentheses! Puzzle: what is -1**2? Why? Logical operators (PP 5.1)

94 Arithmetic operators, precedence exponentiation (**) negation ( unary minus ) (-) multiplication/division (*,/,//=integer division,%=remainder) addition/subtraction (+, - ( binary )) When in doubt, use parentheses! Puzzle: what is -1**2? Why? Logical operators (PP 5.1) comparison: (==,!=)

95 Arithmetic operators, precedence exponentiation (**) negation ( unary minus ) (-) multiplication/division (*,/,//=integer division,%=remainder) addition/subtraction (+, - ( binary )) When in doubt, use parentheses! Puzzle: what is -1**2? Why? Logical operators (PP 5.1) comparison: (==,!=) inequalities: >, <, >=, <=,

96 Arithmetic operators, precedence exponentiation (**) negation ( unary minus ) (-) multiplication/division (*,/,//=integer division,%=remainder) addition/subtraction (+, - ( binary )) When in doubt, use parentheses! Puzzle: what is -1**2? Why? Logical operators (PP 5.1) comparison: (==,!=) inequalities: >, <, >=, <=, basic logic: (and, or, not)

97 Arithmetic operators, precedence exponentiation (**) negation ( unary minus ) (-) multiplication/division (*,/,//=integer division,%=remainder) addition/subtraction (+, - ( binary )) When in doubt, use parentheses! Puzzle: what is -1**2? Why? Logical operators (PP 5.1) comparison: (==,!=) inequalities: >, <, >=, <=, basic logic: (and, or, not) remember your truth tables, e.g. not(a and b) equals (not a) or (not b)

98 a = True; b = False; c=1; d=0 a and b not(a and not b) a and not(b>c) a==c ## careful! not(d) not(c) operator precedence: same issue as order of operations in arithmetic; not has higher precedence than and, or. When in doubt use parentheses...

99 Truth tables A B A and B A or B not A True True True True False True False False True False False True False True True False False False False True

100 Truth tables A B A and B A or B not A True True True True False True False False True False False True False True True False False False False True Logical expressions

101 Truth tables A B A and B A or B not A True True True True False True False False True False False True False True True False False False False True Logical expressions The logical expression: not not a and not b or a is equivalent to ((not (not a)) and (not b)) or a since the operator not takes precedence over the operators and and or.

102 Truth tables A B A and B A or B not A True True True True False True False False True False False True False True True False False False False True Logical expressions The logical expression: not not a and not b or a is equivalent to ((not (not a)) and (not b)) or a since the operator not takes precedence over the operators and and or. So if a = True and b = False then this evaluates to True.

103 Truth tables A B A and B A or B not A True True True True False True False False True False False True False True True False False False False True Logical expressions The logical expression: not not a and not b or a is equivalent to ((not (not a)) and (not b)) or a since the operator not takes precedence over the operators and and or. So if a = True and b = False then this evaluates to True. Since not not a is equivalent to just a for a having value True or False, then the above expression can be simplified to just (a and not b) or a. Can you see that this expression is equivalent to a, i.e, it has value True precisely when a does?

104 From CodingBat: We have two monkeys, a and b, and the parameters a_smile and b_smile indicate if each is smiling. We are in trouble if they are both smiling or if neither of them is smiling. Return True if we are in trouble. monkey_trouble(true, True) -> True monkey_trouble(false, False) -> True monkey_trouble(true, False) -> False More CodingBat problems: squirrel_play cigar_party

105 String operations (PP chapter 4) reference: Python intro section 3.1.2

106 String operations (PP chapter 4) reference: Python intro section Less generally important, but fun

107 String operations (PP chapter 4) reference: Python intro section Less generally important, but fun + concatenates

108 String operations (PP chapter 4) reference: Python intro section Less generally important, but fun + concatenates * replicates and concatenates

109 String operations (PP chapter 4) reference: Python intro section Less generally important, but fun + concatenates * replicates and concatenates in searches for a substring

110 String operations (PP chapter 4) reference: Python intro section Less generally important, but fun + concatenates * replicates and concatenates in searches for a substring One more useful string operation: len(s) returns the length (number of characters)

111 a = "xyz" b = "abc" a+1 ## error a+b b*3 (a+" ")*5 b in a CodingBat problems: make_abba make_tags

112 Indexing and slicing

113 Indexing and slicing Indexing

114 Indexing and slicing Indexing Extracting elements is called indexing a list

115 Indexing and slicing Indexing Extracting elements is called indexing a list Indexing starts from zero

116 Indexing and slicing Indexing Extracting elements is called indexing a list Indexing starts from zero Negative indices count backward from the end of the string (-1 is the last element)

117 Indexing and slicing Indexing Extracting elements is called indexing a list Indexing starts from zero Negative indices count backward from the end of the string (-1 is the last element) Indexing a non-existent element gives an error

118 Indexing and slicing Indexing Extracting elements is called indexing a list Indexing starts from zero Negative indices count backward from the end of the string (-1 is the last element) Indexing a non-existent element gives an error

119 Indexing and slicing Indexing Extracting elements is called indexing a list Indexing starts from zero Negative indices count backward from the end of the string (-1 is the last element) Indexing a non-existent element gives an error

120 Slicing

121 Slicing Extracting (consecutive) sets of elements is called slicing

122 Slicing Extracting (consecutive) sets of elements is called slicing Slicing non-existent element(s) gives a truncated result

123 Slicing Extracting (consecutive) sets of elements is called slicing Slicing non-existent element(s) gives a truncated result Slicing specifies start, end, step (or stride )

124 Slicing Extracting (consecutive) sets of elements is called slicing Slicing non-existent element(s) gives a truncated result Slicing specifies start, end, step (or stride ) Leaving out a bit goes from the beginning/to the end

125 Slicing Extracting (consecutive) sets of elements is called slicing Slicing non-existent element(s) gives a truncated result Slicing specifies start, end, step (or stride ) Leaving out a bit goes from the beginning/to the end Slicing works on strings too!

126 x[:] # everything x[a:b] # element a (zero-indexed) to b-1 x[a:] # a to end x[:b] # beginning to b-1 x[a:b:n] # from a to b-1 in steps of n generate a list of odd numbers from 3 to 15 reverse a string? String slicing practice From CodingBat: first_two first_half