Feb 13, 2019 Notes

IT 211 -- Feb 13, 2019

Review Exercises

What does += mean?
Ans: Is an assignment operator, which is used to update a variable by adding the value on the right to the variable on the left. For example, the expression
```
number_of_customers += 1
```
adds one to the variable on the left. This means the same thing as
```
number_of_customers = number_of_customers + 1
```

Combine the these two lines into one line:

fields = line.strip( ).split(',')
salary = int(fields[4])

Ans:

salary = int(line.strip( ).split(',')[4])
# This is an example of "macho programming."

Find the errors in this script. It is supposed to list the age, city, and salary of an employee whose name is entered at the keyboard. The input file is employees.txt. There are about 13 errors.

desired_name = input("Enter desired name: ")
fin = ("employees.txt", r)
line = fin.readline( )
while line != ""
    fields = line.split (',')
    name = fields[0].strip( )
    age = fields[2].strip( )
    city = fields[3].strip( )
    salary = fields[4].strip( )
    if name = desired_name:
        print("Age: {age}")
        print('City: {city}')
    print(f"Salary: # {salary}")
    close(fin)

What is the output?

for y in range(0, 5):
    for x in range(0, 2 * x):
        print("#", end="")
    print( )

More about User Defined Methods

Method names follow the same spelling rules as local variables: the name must start with a lowercase letter or underscore, and it must consist of lower case letters, underscores, or digits.
These are all properly spelled method names using underscore notation:
```
f  f_5  find_record  update_vehicle_miles
```
You can also use lower camel casing to spell method or instance variable names.
These are all properly spelled method names using lower camel notation:
```
f  f5  findRecord  updateVehicleMiles
```
We will look at these examples next week:

StateRiddles ToFahr OldMacDonald MySqrt
Methods are used for three reasons:
1. Modularization: the various parts of computer software can be developed and tested separately (see the StateRiddles Example).
2. Code Reuse: instead of repeating code in various parts of the software, put the code in a method and then call the method more than once (see the OldMacDonald Example).
3. Encapsulation: the user of a method does not need to understand the code in the method, only how to invoke the method (see the MySqrt Example).
Here are s
def print_greeting(the_person):
Print a greeting to the person whose name is passed in as a parameter.
def print_greeting(the_person):
Return a greeting to the person whose name is passed in as a parameter.
def meters(feet, inches):
Return the length given in feet and inches converted to meters.
Use the fact that one inch == 2.54 centimeters.
def first_char(input_string):
Return the first character of the input string. Return "" if the input string is "".
def to_feet_inches(meters):
Return as a string the length given in meters converted to meters
Use the fact that one inch == 2.54 centimeters.
def is_upper_case(the_string):
Return True if all the letters in the input string are upper case. Return False otherwise.
def num_vowels(the_string):
Return the number of vowels in the input string.
def has_any_vowels(the_string):
Return True if the input string has at least one vowel. Return False otherwise.
def is_all_vowels(the_string):
Return True if the input string consists of all vowels. Return False otherwise.
Test it for the case of the input string "".
def is_factor(number, factor):
Return True if factor is actually a factor of number, False otherwise.
def is_prime(number): return True if number is a prime number, False otherwise.

Project 4

Look at the LetterZ Example.
Rewrite the LetterZ Example so that uses two user defined methods:
```
draw_horizontal_bar( )
draw_diagonal_line( )
```
Look at the LetterHPpm and LetterZPpm Examples.