Description
For this assignment, you will design, implement and test the times module, which contains
class Time. To test the times module, you will develop a program which thoroughly tests
each method in class Time.
1. Your implementation of class Time must be in the file named times.py (and it must be
the only thing in that file).
2. Your implementation of the test program must be in the file named test.py (and it must be
the only thing in that file).
The test program must import your times module and must demonstrate that each method in
class Time is implemented correctly. The output produced by your test program must be
clearly labeled and readable.
In addition, the test program must contain at least one function (besides function main), and that
function must have at least one parameter which is a Time object and which it uses in producing
some output. The test program must call your function.
Specifications for Class Time
1. Method __init__ initializes a Time object. The following examples illustrate the method’s
behavior, where the desired time is shown as a comment:
A = times.Time( 6, 15, 30, 5 ) # 06:15:30+05
B = times.Time( 8, 9, 15, -4 ) # 08:09:15-04
C = times.Time( 14, 20, 45 ) # 14:20:45+00
D = times.Time( 23, 59 ) # 23:59:00+00
E = times.Time( 12 ) # 12:00:00+00
F = times.Time() # 00:00:00+00
The method will validate all parameters. If the method is unable to construct a valid Time
object, it will raise a ValueError exception.
2. Methods __str__ and __repr__ return a str object which is a printable representation of a
Time object. Assuming the Python statements above, the following examples illustrate the
behavior of the methods, where the desired str object is shown as a comment:
str(A) # “06:15:30+05”
repr(B) # “08:09:15-04”
str(C) # “14:20:45+00”
repr(D) # “23:59:00+00”
str(E) # “12:00:00+00”
repr(F) # “00:00:00+00”
3. Method from_str accepts a str object (representing the desired time) and changes the
value of the Time object. For example:
T = times.Time()
T.from_str( “06:15:30+05” ) # 06:15:30+05
The method will validate the parameter. If the parameter does not represent a valid Time object,
it will raise a ValueError exception.
4. Method get_as_local returns a str object which is a printable representation of the time
based on a 12-hour “local” clock (which leaves out the time zone). Assuming the Python
statements above, the following examples illustrate the behavior of the method, where the
desired str object is shown as a comment:
A.get_as_local() # “06:15:30 AM”
B.get_as_local() # “08:09:15 AM”
C.get_as_local() # “02:20:45 PM”
D.get_as_local() # “11:59:00 PM”
E.get_as_local() # “Noon”
F.get_as_local() # “Midnight”
5. The class will support six forms of comparison between two Time objects. For example:
T1 = times.Time( 7, 35, 15, -6 )
T2 = times.Time( 7, 21, 30, -5 )
T1 == T2 # False
T1 != T2 # True
T1 < T2 # False
T1 <= T2 # False
T1 T2 # True
T1 = T2 # True
The methods will raise a TypeError exception if the second parameter is not a Time object.
6. The class will support the addition of a Time object and an int object (which represents a
number of seconds). For example:
T1 = times.Time( 23, 15, 0, 5 ) # 23:15:00+05
T2 = T1 + 300 # 23:20:00+05
T3 = T1 + 3600 # 00:15:00+05
T4 = T1 + -90000 # 22:15:00+05
The method will raise a TypeError exception if the second parameter is not an int object.
7. The class will support the subtraction of two Time objects, where the result is the number of
seconds by which the two times differ. For example:
T1 = times.Time( 14, 20, 45 ) # 14:20:45+00
T2 = times.Time( 14, 18, 15 ) # 14:18:15+00
T1 – T2 # 150
T2 – T1 # -150
T1 = times.Time( 7, 35, 15, -6 ) # 07:35:15-06
T2 = times.Time( 7, 21, 30, -5 ) # 07:21:30-05
T1 – T2 # 4425
T2 – T1 # -4425
The method will raise a TypeError exception if the second parameter is not a Time object.
Assignment Notes
1. Items 1-10 of the Coding Standard will be enforced for this project.
2. It is critical that your methods use the specified names, number and type of parameters.
3. The quality of your test program is important. It must be thorough in showing that each
method operates correctly for a set of parameter values which cause the method to execute
different paths (sequences of statements). Output must be clearly labeled indicating the
expression that was evaluated and the outcome.
4. The keyword raise is used to raise an exception. For example:
raise TypeError
See subsection 14.6.1 of the Punch and Enbody textbook.
5. For this assignment, midnight is defined to be 00:00:00 (rather than 24:00:00).
