Programming for engineers in python
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Programming for Engineers in Python. Recitation 4. Agenda. Sample problems Hash functions & dictionaries (or next week) Car simulation. A function can be an argument. def do_twice (f): f () f() def print_spam (): print 'spam' >>> do_twice ( print_spam ) spam spam.

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Programming for Engineers in Python

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Programming for engineers in python

Programming for Engineers in Python

Recitation 4


Agenda

Agenda

  • Sample problems

  • Hash functions & dictionaries (or next week)

  • Car simulation


A function can be an argument

A function can be an argument

defdo_twice(f):

f()

f()

defprint_spam():

print'spam'

>>> do_twice(print_spam)

spam

spam


Fermat s last theorem

Fermat’s last theorem

  • Fermat’s famous theorem claims that for any n>2, there are no three positive integers a, b, and c such that:

  • Let’s check it!

    defcheck_fermat(a,b,c,n):

    if n>2 and a**n + b**n == c**n:

    print"Fermat was wrong!"

    else:

    print"No, that doesn't work"

Pierre de Fermat

1601-1665


Fermat s last theorem1

Fermat’s last theorem

>>> check_fermat(3,4,5,2)

No, that doesn't work

>>> check_fermat(3,4,5,3)

No, that doesn't work

  • Dirty shortcut since 1995:

    defcheck_fermat(a,b,c,n):

    print"Wiles proved it doesn’t work"

Sir Andrew John Wiles

1953-


Cumulative sum

Cumulative sum

  • For a given list A we will return a list B such that

    B[n] = A[0]+A[1]+…A[n]

  • Take 1:

    defcumulative_sum(lst):

    summ = [ lst[0] ] * len(lst)

    for i inrange(1, len(lst)):

    summ[i] = summ[i-1] + lst[i]

    returnsumm

  • Take 2:

    defcumulative_sum(lst):

    return [sum(lst[0:n]) for n inrange(1, len(lst)+1)]


Estimating e by it s taylor expansion

Estimating e by it’s Taylor expansion

frommath import factorial, e

term = 1

summ= 0

k = 0

whileterm > 1e-15:

term = 1.0/factorial(k)

summ+= term

k += 1

print"Python e:", e

print“Taylor’s e:", summ

print “Iterations:”, k

Brook Taylor, 1685-1731


Estimating by the basel problem

Estimating π by the Basel problem

frommath import factorial, pi, sqrt

term = 1

summ= 0

k = 1

whileterm > 1e-15:

term = 1.0/k**2

summ+= term

k += 1

summ = sqrt(summ*6.0)

print"Python pi:", pi

print“Euler’s pi:", summ

print “Iterations:”, k

Leonard Euler,

1707-1783


Ramanujan s estimation optional

Ramanujan’sπ estimation (optional)

frommath import factorial, pi

term = 1

summ= 0

k = 0

whileterm > 1e-15:

term = factorial(4.0*k) / factorial(k)**4.0

term *= (1103.0+26390.0*k) / 396.0**(4.0*k)

summ += term

k += 1

summ =1.0/(summ * 2.0*2.0**0.5 / 9801.0)

print"Python Pi:", pi

print"Ramanujan Pi:", summ

print “Iterations:”, k

SrinivasaRamanujan,

1887-1920


Triple double word

Triple Double Word

  • We want to find a word that has three double letters in it, like aabbcc (which is not a word!)

  • Almost qualifiers:

    • Committee

    • Mississippi

  • Write a function to check if a word qualifies

  • Write a function that reads a text file and checks all the words

  • Code: http://www.greenteapress.com/thinkpython/code/cartalk.py

  • Corpus: http://www.csie.ntu.edu.tw/~pangfeng/Fortran%20examples/words.txt


Pygame

PyGame

  • A set of Python modules designed for writing computer games

  • Download & install:

    http://pygame.org/ftp/pygame-1.9.2a0.win32-py2.7.msi


Car game

Car game

  • Control a car moving on the screen

  • YouTube demo: http://www.youtube.com/watch?v=DMOj3HpjemE

  • Code: https://gist.github.com/1372753 or in car.py

  • Car controlled by

    arrows

  • Honk with Enter

  • Exit with ESC


Todo list

ToDo List:

  • Fix stirring problem

  • Honk by pressing space

  • Car will go from the bottom to top and from one side to the other (instead of getting stuck)

  • Switch to turtle!


2 players car game

2 players car game

  • Collision avoidance simulator:

    • When the cars are too close one of them honks

    • Players need to maneuver the cars to avoid honks

  • Code: https://gist.github.com/1380291 or cars.py

  • Red car controlled by arrows

  • Blue car controlled by z, x, c, s


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