Download VI. String Methods.

Chapter 2- Types, Variables, Memory, Simple Input and Output
I. Basic Programming
Input
Process
Output
II. Strings
A. Using String
# Demonstrates the use of quotes in strings
print("Program 'Game Over' 2.0")
print("Same", "message", "as before")
print("Just",
"a bit",
"bigger")
print("Here", end=" ")
print("it is...")
print(
"""
_____
___
___ ___ _____
/ ___| / | / |/ | | ___|
||
/ /| | / /| /| | | |__
| | _ / ___ | / / |__/ | | | __|
| |_| | / / | | / /
| | | |___
\_____/ /_/ |_| /_/
|_| |_____|
_____ _ _ _____ _____
/ _ \ | | / / | ___| | _ \
| | | | | | / / | |__ | |_| |
| | | | | | / / | __| | _ /
| |_| | | |/ / | |___ | | \ \
\_____/ |___/ |_____| |_| \_\
)
"""
a. When you put quotes around something, Python takes it literally. It prints
exactly what is in the quotes. You can use double quotes or single quotes for
a string.
i. teacher = “Mrs. Heineman” or teacher = ‘Mrs. Heineman’
b. You can print multiple values with a comma in-between strings for example:
print ( “Same”, “message”, “ as before”) A space is automatically placed
between the words.
c. Concatenate- adding together strings
i. print “cat” + “dog would show catdog
ii.
open Silly string program
d. Long Strings- triple quoted string
i. Use when you have several lines of text that you want displayed
together
ii. longString=””” Sing a song of sixpence, a pocket full of rye,
Four and twenty black birds baked in a pie.
When the pie was open, the birds began to sing.
Wasn’t that a dainty dish to set before the king?””
B. Escape Sequences with Strings
a. allows you to put special characters into your strings.
b. made up of two characters: a backslash followed by another character.
# Fancy Credits
# Demonstrates escape sequences
print("\t\t\tFancy Credits")
print("\t\t\t \\ \\ \\ \\ \\ \\ \\")
print("\t\t\t\tby")
print("\t\t\tMichael Dawson")
print("\t\t\t \\ \\ \\ \\ \\ \\ \\")
print("\nSpecial thanks goes out to:")
print("My hair stylist, Henry \'The Great,\' who never says \"can\'t.\"")
# sound the system bell
print("\a")
input("\n\nPress the enter key to exit.")
Sequence
\\
\’
\”
\a
\n
\t
Description
Backslash, prints one backslash
Single quote, prints one single quote
Double quote, prints one double quote
Bell, sounds the system bell
Newline, moves cursor to beginning of
next line
Horizontal tab, moves cursor forward
one tab
III. Math in Python
Mathematical Operations in Python
Operator
Description
+
Addition
Subtraction
*
Multiplication
/
Division ( true)
//
Integer Division
%
Modulus
**
Exponentiation
Evaluate the expression.
1. 3 + 5
Example
7+3
7-3
7*3
7/3
7//3
7%3
2**3
Evaluates to
10
4
21
2.33333…
2
1
8
5. 10//3
2. -2*8
6. 10 % 3
3. 3**2
7. 20/3
4. 10/3
8. 20.0/3.0
Order of Operations in Python- same as mathematics
- unary
( )Parenthesis
**exponents
*,/,//,% multiplication, division, integer division, modulus ( left to right evaluation)
+,- addition and subtraction ( left to right evaluation)
Evaluate using order of operations.
1. 8 + 3*(6 + 1)
2. 3**3 + 4 * -2 – 3
3. 5 + 8 /4 * 3
4. (2 + 3) ** 2 -10%2
5. 100%34 + 30/5
6. 6 + 2 – 5 * 2 +20%6
Data Types
1. Integers …-3, -2, -1, 0, 1, 2, 3, ….
2. Decimal- floating point numbers 1.24, -0.3789 etc
3. Strings- characters contained in “ ” or ‘ ’
Short cut for Increments and Decrements- Augmented Assignment Operators
If you wrote the coding
score= score + 1 This line would add one to the value of score
Python short cut score+=1 means the same thing as the line above.
score-=1 would subtract one from the value of score
Operator
+=
-=
*=
/=
%=

Example
x+=5
x-=5
x*=5
x/=5
x%=5
Is Equivalent to
x=x+5
x=x-5
x=x*5
x=x/5
x=x%5
See Word Problem Program
IV. Using Variables
a. Variable exists when you assign a name to a value. A variable is stored in
memory.
Example of an assignment statement
teacher= “Mrs. Heineman”
print( teacher)
The result would be Mrs. Heineman on the screen.
b. The equal sign is used to give the variable a value.
c. Variables can be created for characters as well as numbers.
d. Rules for Variable Names
i. Can have letters, numbers and underscore
ii. Python is case sensitive
iii. Must start with letter or underscore
iv. No spaces
v. Use descriptive names
vi. Name convention - intercap method- start with lowercase
i. firstName
ii. middleInitial
vii. try to keep within 15 characters
e. Assigning variables
i. The variable name goes on the left side of the equal sign.
ii. firstName=”John”
V. Getting User Input
#Personal Greeter
name=input(“Hi. What is your name?”)
print(name)
print(“Hi”, name)
input(“\n\nPress enter to exit.”)
Input is a function that allows the user to enter in information and store it in a
variable. Input function always returns a string.
VI. String Methods.
Look at the coding below. Predict what will happen next to each line. Then type
and run program
# Demonstrates string methods
# quote from IBM Chairman, Thomas Watson, in 1943
quote = "I think there is a world market for maybe five computers."
print("Original quote:")
print(quote)
print("\nIn uppercase:")
print(quote.upper())
print("\nIn lowercase:")
print(quote.lower())
print("\nAs a title:")
print(quote.title())
print("\nWith a minor replacement:")
print(quote.replace("five", "millions of"))
print("\nOriginal quote is still:")
print(quote)
input("\n\nPress the enter key to exit.")
String Methods
Method
upper()
lower()
swapcase()
capitalize()
title()
strip()
replace(old, new[,max])
Description
Returns uppercase version of string
Returns lowercase version of string
Returns a new string where the case of
each letter is switched. Uppercase
becomes lowercase and lowercase
becomes uppercase.
Returns a new string where the first
letter is capitalized and the rest are
lowercase.
Returns a new string where the first
letter of each word is capitalized and all
others are lowercase.
Returns a string where all the
whitespace (tabs, spaces, and newlines)
at the beginning and end is removed.
Returns a string where occurrences of
the string old are replaces with the
string new. The optional max limits the
numbers of the replacement.
Examples :
name.lower()- would return the name in lower case
name.upper()- would return the name in upper case.
VI. Converting Values

Run Trust Fund Buddy Bad
Logical Errors- program produces unintended results but does not crash.
A. Converting Values
 Run Trust Fund Buddy Good program
Function
Description
float(x)
Returns a floating point value by
converting x.
int(x)
Returns an integer value by
converting x
str(x)
Returns a string value by
converting x.
Example
float(“10.0”)
Returns
10.0
int(“10”)
10
str(10)
‘10’
Review Questions
Name___________________________
1. How do you tell Python that a variable is a string instead of a number?
2. Once you have created a variable, can you change the value that is assigned
to it?
3. With the variables teacher and Teacher, are they the same?
4. Is “Hello” the same as ‘Hello’ in Python?
5. Which of the following is not a correct variable name? Why?
a. Teacher2
b. 2Teacher
c. teacher_25
d. TeaCher
6. Is “10” a number or a string?
7. Is ‘4’ the same as 4 to Python?
8. State the output.
name=”John Doe”
print (name.lower())
9. Fix the statement so it converts to stated data type.
a. age=input(“Enter age”) #convert age to an integer
b. hourlyWage=input(“Enter wage”)
10. Write a valid variable name for the following – state its data type.
a. Your grade point average.
b. Book title
c. Number of students in school
d. Your phone number
Chapter 2 Programs.




For each program make comments at the top with your name and the
program’s name.
Use proper variable names
Make output “look nice”. It should never be just a number. For example:
print(“The total amount is $”,total)
Save all programs with proper name in your folder.
1. Make a program that assigns your first name to the variable firstName; last
name assigned to variable lastName and then display your first and last name
with a space inbetween.
2. Tipper Program- Write a program where the user enters the total of the bill
from a restaurant order. The program should then display two amounts; a
15% tip and a 20% tip.
3. Write a car salesman program where the user enters the base price of a car.
The program should add on extra fees such as tax, dealer prep and
destination charge. Make the tax be 7% of the cost of the car, dealer prep is
$250 and destination charge is $130.50. Display the actual price of the car
once everything is added in.
4. Write a program that has the user input an amount in change less than one
dollar. The program should output the number of quarters, dimes, nickels
and pennies used for that amount. Assume it will give the most possible of
the largest coins. For example: 92 is the inputted value.
Hint: you need to use modulus.
Output:
The number of quarters: 3
The number of dimes: 1
The number of nickels: 1
The number of pennies: 2