Introduction to Mathematical and Scientific Programming TUTORIAL WEEK 1 (MATH 1MP3) Winter 2019

Transcription

1 TUTORIAL WEEK 1 Introduction to Mathematical and Scientific Programming (MATH 1MP3) Winter 2019

2 Important Links 1- The Course Website 2- Python 3- Anaconda ( Python + Packages + Spyder )

3 4- McMaster Online Jupyter : ( Jupyter Notebook + Python + Anaconda Packages) : 5- Codelab (Examples) 6- CodingBat (Examples)

4 Anaconda and Spyder Anaconda contains Python 3 and all the associated libraries we use in the course. Spyder is an IDE ( integrated development environment) that points out errors in your code (e.g. syntax highlighting) and allows debugging of more complex code. The easy way to get up and running with Spyder on any of the supported platforms is to download it as part of the Anaconda. So that, If the Anaconda is installed, the Spyder would be available on the system.

5 Anaconda Installation : How to Install ANACONDA Follow the installation instructions for your operating system.

6 Spyder

7 Jupyter

8 General Advice: If you have a Python questions try searching the question on the websites like before ing the TAs.

9 Review Python Basics Assignment: = is the assignment operator, it assigns a value to a variable(s): variable = value

10 Examples: x = 14 print("first x: ", x) x = 34 x Result : first x: ## multiple assignments in one statement y, z = (3,4) print("y: ", y, " z: ", z) Result : y: 3 z: 4 Y = 14 ; Z=Y print(" Y: ", Y) Y = " Hello ", print(" Y: ", Y) print(" Y: ", Y, " Z: ", Z) Result : Y: 14 Y: (' Hello ',) Y: (' Hello ',) Z: 14

11 Standard Data Types The data stored in memory can be of many types. Python has Six standard data types: 1. Numbers integer (int) floating-point (float) 2. boolean (bool: True or False) 3. String defined as "..." or str(...) 4. List 5. Tuple 6. Dictionary Will be explained in the following sessions.

12 Example x = 208 print("type(x): ", type(x)) y = print("type(y): ", type(y)) ## converts int to float print("type(y/x): ", type(y/x)) print("the actual value of y/x:",y/x) print("type(int(y/x)): ", type(int(y/x)) ) print("the integer version of y/x is:",int(y/x)) f = False t = True print("t's type: ", type(t)) Result : type(x): <class 'int'> type(y): <class 'float'> type(y/x): <class 'float'> the actual value of y/x: type(int(y/x)): <class 'int'> the integer version of y/x is: 1 t's type: <class 'bool'>

13 Arithmetic operators (The table is for : com/python/python_basic_ operators.htm )

14 Examples: ## boolean's become int's when added arithmetic operators are applied to them f = False t = True print("f+t: ", f+t) print("type(f+t): ", type(f+t)) ## division print("2.12 / 2 :", 2.12 / 2) ## integer division print("2.12 // 2 :", 2.12 // 2) Result: f+t: 1 type(f+t): <class 'int'> 2.12 / 2 : // 2 : % 2 : ## remainder or modulus print("2.12 % 2 :", 2.12 % 2)

15 Order of operation Important to understand for tests/exams. Is a common source of errors. General advice: When programming, ignore it and add parentheses to your expression.

16 Examples: ## notes example print("-1**2: ", -1**2) ## brackets print("(-1)**2: ",(-1)**2) ## bracketing x = 3 print("bracketing: ", ((x**2)+(x*2)) / (-x) ) Result: -1**2: -1 (-1)**2: 1 bracketing: -5.0 no bracketing: 7.0 ## no bracketing print("no bracketing: ", x**2+x*2/-x)

17 Logical operators : These operators compare the values on either sides of them and decide the relation among them. They are also called Relational operators. == tests equality Don t use = to test equality by accident!= tests not equal (The table is for : ython/python_basic_operators.ht m )

18 Examples: f = False t = True ## are they (t & f) equal? print("t == f: ", t == f) ## are they not equal? print("t!= f: ", t!= f) ## another example: x=3 y=4 print("x == y: ", x == y) print("x!= y: ", x!= y) Result: t == f: False t!= f: True x == y: False x!= y: True

19 Also, There are some other logical operators supported by Python language (Boolean Operators): NOT OR AND (The table is for : hon/python_basic_operators.htm )

20 Boolean Operators: The expression A and B is true if both A is true and B is true, and false if either is false. The expression A or B is true if either A is true or B is true, and false if both are false. The expression not A is true if A is false, and false if A is true. Example: not X or Y and Z means (not X) or (Y and Z)

21 Examples: ## not operator print("not(t == f): ", not(t == f)) ## and, or operators print("t and f: ", t and f) print("t or f: ", t or f) print("not(t or f): ",not(t or f)) Result: not(t == f): True t and f: False t or f: True not(t or f): False

22 Strings "+" = concatenates "*" = replicates and concatenates Strings are like lists of characters (you will learn about lists soon). Indexing starts at 0 - the first value in the string/list is at location 0

23 Examples: s1 = "Hello World" s2 = "lo ## concatenates three strings print(s1 + "---" + s2) ## concatenates two strings and repeats the result three times: Result: Hello World---lo Hello World:Hello World:Hello World: tests if s2 in s1: True print((s1+":")*3) print("tests if s2 in s1: ", s2 in s1)

24 print("s1: ", s1) ## First entry of s1 print("first character: s1[0]: ", s1[0]) ## 4th to 6th position print("s1[3:7]: ", s1[3:7]) ## Note the end digit is +1 from the index you want, here we went from the 4 position to the 6 th position which is specified by the 7th index ## last two characters print("last two characters: s1[-2:]:", s1[-2:]) ## Everything but the last two characters print("up to the last two characters: s1[:-2]:", s1[:-2]) ## print every second character print("every second character: s1[::2]", s1[::2]) Result: s1: Hello World First character: s1[0]: H s1[3:7]: lo W Last two characters: s1[-2:]: ld Up to the last two characters: s1[:-2]: Hello Wor Every second character: s1[::2] HloWrd Reverse s1: s1[::-1]: dlrow olleh ## Reverse a string print("reverse s1: s1[::-1]: ", s1[::-1])

25 Acknowledgement: Thanks to Peter Tait. This tutorial was written for Math 1MP3 winter 2019 and it was written and was completed based on the fall 2018 Math 1MP3 course s tutorials which were provided by Peter Tait.