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CS 1113-300 Introduction to Programming

Fall 2016

Exam 3 Review - Part 2 (Python) Friday, December 2nd, 2016

Ahmed Ibrahim

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Course Evaluation

Please take a few minutes to submit your course evaluation on Collab

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Touch-up

• Alexander’s office hours are on Sunday 2-5.

• Any problems with using py in MATLAB, Piazza.

• P3 is due by the end of Monday 12/5.

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About the Test• Thursday, December 2, 2016.

• Your lecture hall (Thornton E316).

• Time: 3 hours (9:00AM - 12:00PM).

• Format: writing on paper; bring pen/pencil (nothing else).

• Bubble your first page (2 points).

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About the Test• Students with accommodations should contact the SDAC to

schedule a time slot any time on Wednesday to take the test.

• There is Office Hours on Monday and Tuesday.

• No Office Hours will be held on Wednesday. (You can still e-mail and we’ll figure something out)

• Be here early!

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What is on the Test• Python:

Arithmetic / Boolean / Strings / Expression Evaluation / Conditions / Loops (while / for) / Functions / Lists Call-by-value / Call-by-reference / Files / … etc (NO DICTIONARIES / RANDOM / Input Validation)

• MATLAB: Arithmetic / Boolean / Strings / Expression Evaluation / Conditions / Loops (while / for) / Spacing / Functions Multiple Output / … etc (Simple Plotting)

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Type of Questions• True / False (Python & MATLAB)

• Multiple Choice (Python & MATLAB)

• Expression Evaluation (Python & MATLAB)

• Short Answer & Tracing (Python & MATLAB)

• Writing functions (Python & MATLAB)

• One “big” coding question (!?)

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Questions?

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Remember• The algorithm must be:

- Unambiguous - Executable- Terminating

• Control Structures: sequence / condition / loop / subprogram

• Types of Errors: Syntax / Logical / Runtime

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Strings• The split() method:

fn, ln = input("Please enter your name: ").split() name_list = input("Please enter your name: ").split()

• String indexes:what is str[3]? what is str[-1]? what is str[len(str)-1]?what is str[ : 5]? what is str[3:7]? what is str[11 : ]?

str="WelcometoCS1113!"

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String Replication / Concatenation

• String Replication:

• String Concatenation:

• String Length:

str="10"*3#"101010"

len(str)#GETSTHELENGHTOFTHESTRING

str="10"+"3"#"103"

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Boolean Operators• Evaluate the following expressions:50 == “50” 0 < temp < 1006 > 2 and not ( 7 > 5 ) 6 > 2 or not ( 7 < 5 )

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Functions• Simpler code

• Code reuse

• Write the code once and call it multiple times

• Better testing and debugging

• Faster development

• Easier facilitation of teamwork

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Functions

• Can have 0 or more arguments

• Number of parameters passed MUST be the same as the number of args - unless arguments are optional!

• Can have 0, 1 or multiple return values

• Local variables can’t be accessed outside the function

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Functions• A function starts with a header def function_name (0_or_more_arguments): # code # x = 10 -> local variable # code # return statement # code

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Pass by Value1 2

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Pass by Reference1 2

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Lists#1:Creatingalist values=[32,54,67.5,29,35,80,115,44.5,100,65]

#2:Accessingalistelement values[5]=87

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Out of Range Errors• Perhaps the most common error in using lists is accessing a nonexistent

element

• If your program accesses a list through an out-of-range index, the program will generate an exception at run time.

values=[2.3,4.5,7.2,1.0,12.2,9.0,15.2,0.5] values[8]=5.4 #Error––valueshas8elements, #andtheindexcanrangefrom0to7

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• The concatenation of two lists is a new list that contains the elements of the first list, followed by the elements of the second

• Two lists can be concatenated by using the plus (+) operator:

List Concatenation

myFriends=["Fritz","Cindy"] yourFriends=["Lee","Pat","Phuong"]

ourFriends=myFriends+yourFriends #SetsourFriendsto["Fritz","Cindy","Lee","Pat","Phuong"]

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• Replication of two lists is a new list that contains the elements of the first list, followed by the elements of the second.

• Results in the list [1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2 ,3]

• The integer specifies how many copies of the list should be concatenated

• One common use of replication is to initialize a list with a fixed value

List Replication

month_in_quarter=[1,2,3]*4

monthly_scores=[0]*12

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Looping Over the List• Given a list that contains n elements, you can loop over the

list using one of the following ways:

#listindexusedforiinrange(len(values)):print(i,values[i])

#indexvaluesnotneeded(traverselistelements)forelementinvalues:print(element)

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Loop Over a Tabletable=[[3,4,5],[6,7],[8,9,10,11,12]]

forrowinrange(len(table)):forcolumninrange(len(table[row])):print(table[row][column])

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Reading From a File - for

infile=open("input.txt","r")

forlineininfile:#Processtheline.

infile.close()

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Writing to a File• To open a file for writing, you provide the name of the file as the first

argument to the open function and the string "w" as the second argument:

• If the output file already exists, it is emptied before the new data is written into it

• If the file does not exist, an empty file is created

outfile=open("output.txt","w")outfile.write("text\n")#stringonly

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Practice Coding on Paper• How to practice?Try re-solving the Homeworks and Lab problems on paper without looking at your code or textbook. Try re-solving the lecture code on paper without looking at your notes or the lecture slides. Start with: HW4 / HW5 / HW6 / HW7 / HW8 / Lab8 / Lab10