Description
1 C programming
1 # tuple
2 days = (‘Monday’,‘Tuesday’,‘Wednesday’,‘Thursday’,‘Friday’,‘Saturday’, ‘Sunday’)
3 # list
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students = [‘Sam’, ‘Tom’, ‘Laura’, ‘Dave’, ‘Sarah’]
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print(students[2])
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students.append(‘Catherine’)
7 del students[3]
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print(students[2:4])
9 # dictionary
10 gradebook = {‘Andrew Parson’: [ ‘a-‘, ‘b’, ‘c+’], \
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‘Paul Black’: [ ‘a-‘, ‘b+’, ‘a+’ ]}
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del gradebook[‘Andrew Parson’]
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gradebook[‘Angela Tree’] = [‘d’, ‘c-‘, ‘f’]
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gradebook
Loops and conditional statements
In the rest of the lab it is recommended to write the code is a text editor and then run it from the terminal using the command python filename.py.
In Python any code must be indented. A program that is not properly indented will not run.
If statement
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#!/usr/bin/python
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a=0; b=1; c=4
3 if a < 3:
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print(a)
5 if a < 3 and b > 0:
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print (c)
7 elif b == –1:
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print(b)
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else:
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print(a)
Ternary operator
1 a=0; b=1
2 a if a < b else b
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#!/usr/bin/python
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a=0
3 while a != 0:
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a = input(“Input a number: “)
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a+=1
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print(a)
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print(‘Bye’)
For loops
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#!/usr/bin/python
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for i in list(range(3,12,2)):
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print(i)
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students = [‘Sam’, ‘Tom’, ‘Laura’, ‘Dave’, ‘Sarah’]
5 for i in students:
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print(“{} is a student”.format(i))
Defining and calling functions
Defining functions requires to use the keyword def. Python programs do not need to define a main function.
Simple functions
1 def gm(course):
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return “Good morning “ + course + “!”
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course=‘ve477’
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message=gm(course)
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print(message)
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print(gm(input(“Input course code: “)))
7 def list(students,courses):
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for i in students:
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print(i)
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del students[1]
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courses.append(‘ve281’)
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return students,courses
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c = [‘ve477’, ‘ve370’]
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s = [‘Sam’, ‘Tom’, ‘Laura’, ‘Dave’, ‘Sarah’]
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a,b=list(s, c)
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print(students)
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print(a, b, d, e)
1 def list(students,courses):
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for i in students:
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print(i)
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del students[1]
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courses.append(‘ve281’)
6 return students,courses
7 c = [‘ve477’, ‘ve370’]
8 s = [‘Sam’, ‘Tom’, ‘Laura’, ‘Dave’, ‘Sarah’]
9 # the input order can be changed
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d,e=list(courses=c,students=s)
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# define a function with a variable number of input
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def varin(*args):
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return args
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varin(1,2,3); varin(1); varin(1,2,3,4,5,6,7,8)
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# define a function with a variable number of keywords
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def varkw(**kwargs):
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return kwargs
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varkw(students=[‘Sam’, ‘Tom’], courses=[‘ve477’, ‘ve370’],\
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sports=[‘tennis’, ‘soccer’])
First class functions
In Python a function can be passed as an argument or returned by a function.
1 def adding(x):
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def add(y):
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return x+y
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return add
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add_2=adding(2)
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print(add_2(123))
List, set, and dictionary comprehensions
A list, set, or dictionary comprehension is a way to construct new lists, sets, or dictionaries from existing ones. It follows a syntax similar to set definition in mathematics.
1 [i+3 for i in [1, 2, 3]]
2 [5*i for i in [3, 4, 5, 6, 7] if i < 5]
3 {x for x in ‘abcdef’ if x not in ‘abc’}
4 {i: i**3 for i in range(2,10,3)}
A Lambda function is a Python facility allowing to embed a function within the code. It can be viewed as an “embedded function” which does not need to be declared using def.
Basic use
1 l = [lambda x: x ** 2, lambda x: x ** 3, lambda x: x ** 4]
2 for i in l:
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print(i(2))
4 min = (lambda x, y: x if x < y else y)
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min(12,16)
Lambda and map functions
1 # distances in Miles
2 mi=[ 123, 2, 45, 87.2, 192 ]
3 # distances in km
4 km=map(lambda x: x*1.609344,mi)
5 for i in km:
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print(i)
Lambda and filter functions
1 gradebook = {‘Andrew Parson’: [ 55, 40, 60], ‘Paul Black’: [ 85, 80, 95 ]}
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list(filter(lambda x: x < 60, gradebook[‘Andrew Parson’]))
Exercise
Python 3 short practice:
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Construct more complex examples showing how to use:
– Lambda functions with map(), and filter()
– List, set, and dictionary comprehensions
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Write a phone book application, where the user can add, remove, and edit entries.
