Objectives Objectives Example Problem: Simple Statistics Sample ...

! " "

#

# $ # #

' ! &

"

% &

# ' #

#

&

,) ! "

-

'

' #

#

)

&

.

& "

# #

#

*

) #

&

/

' 0

(

23

!'

' '

4

+

" * # '

# average4.py # A program to average a set of numbers # Illustrates sentinel loop using empty string as sentinel def main(): sum = 0.0 count = 0 xStr = raw_input("Enter a number ( to quit) >> ") while xStr != "": x = eval(xStr) sum = sum + x count = count + 1 xStr = raw_input("Enter a number ( to quit) >> ") print "\nThe average of the numbers is", sum / count

' # 3 0 6 & ' '

0# 0 ) !

&

main() 1

Python Programming, 1/e

5

1

"

! * 8 9 + 5 ; ( ' ! ' !

: 5 5 '

!

"

& #

! !

!

& #

& & !

"

#

# ' &

!

)

&

0 ' )

&

7

"

!

( x − xi )

s=

n −1

x


# ! &

!

> '

& + 5 ;

(&

# *

# =

" "

#

5&4 #

!

( 6.8 − 2 ) + ( 6.8 − 4 ) + ( 6.8 − 6 ) + ( 6.8 − 9 ) + ( 6.8 − 13) 2

#

2

2

2

2

= 149.6

149.6 s= = 37.4 = 6.11 5 −1 ;

?

2 . ! $'

# .

3

!

'

@ .

'

Python Programming, 1/e

3 '

% . !

'

*

&

& #!

3 0 ' &

'

A

'

# #!

&

2

2

2

:

B

* #

* ?

(

C

#!

#

&

s& .

! *

8

*

* ' #

0

sum = 0 for i in range(n): sum = sum + s[i]

#

& D 9

!

!

*

!

&

n −1 i =0

*

0 &

si (

2

+

2 * * $ & & s%

#

'

&"

# ! $ & & s[i]%&

) #)

'

9 !

' # '

0

& & #

* &

& & 1

2

2 ,) # ' 3! & " # '

E *F K E *F E *F JE 8 ) F I E *FG H $E *F% 2 E *FGH # E! F E *F E ) F E *F -

)

0 # ! *

>>> lst = [1,2,3,4] >>> 3 in lst True

$D

&

% 7

Python Programming, 1/e

5

4

3

2

2

" '

)

#

#

0

&"

sum = 0 for x in s: sum = sum + x

1?

L 0 >>> >>> 4 >>> >>> [1, >>> >>> [1,

9 zeroes = [0] * 50

lst = [1,2,3,4] lst[3] lst[3] = "Hello“ lst 2, 3, 'Hello'] lst[2] = 7 lst 2, 7, 'Hello']

;

?

2

2

2

-

# &

nums = [] x = input('Enter a number: ') while x >= 0: nums.append(x) x = input('Enter a number: ')


+7

Python Programming, 1/e

# 0

' 0' sort '

& . ' 0# ' & " / ' 0 ' -1 0 1&

cmp("a","b")

'

+5

'

' sort

cmp8

'

+4

8

2

#

2

.

cmp #

8

data.sort(cmpGPA) N ' 3 # cmpGPA&

&

def cmpGPA(s1, s2): return cmp(s1.gpa(), s2.gpa()

.

'

" cmpGPA cmpGPA

' # $cmpGPA% data.sort(cmpGPA)

#

&

'

()3

#

3 ' ' '

& +;

1?

' 2 O O

#

2

&

# #

&

0

$% Q " #

# # # B # #&

$# $# BG H # & $

%$#' # B # # &' #&

$ $#

B # Q % B & $ # B # ' Q "

% PP %

0

# P 'P %

$

% $ &

# #

/ $

/

%%

#UU

%

'U



%$&

dieView 0

$%%

/ Q $Q ,

#

$#

%

/ % 'U $Q , Q % $ #

UUBB P UU

#

& ' ! 0 pip2 pip3 C

# % '

#

!

Q#

UUP



%$$Q R S R# S R# S QR $ & N $% & < $% & T $%%%

%$# 0# ! # # 0#

pip1

1

1

'

'

2

2

.

#' A

' #

! 0

'

& pips = [] pips.append(self.__makePip(cx-offset,cy-offset) pips.append(self.__makePip(cx-offset,cy) … self.pips = pips

self.pip1 = self.__makePip(cx, cy)

__makePip DieView

# !

&

1(

Python Programming, 1/e

1+

9

'

'

2

2 !

#'

0

&

#

self.pips = [self.__makePip(cx-offset,cy-offset), self.__makePip(cx-offset,cy), … self.__makePip(cx+offset,cy+offset) ]

"

! #

2

for pip in self.pips: pip.setFill(self.background)

#

VH3& 0 &

0 0

0 ' '

&

"

!

0

#

!

'@ 11

15

'

'

2

2

.

0 &

< 0

3

!

'

0 for i in [0,3,6]: self.pips[i].setFill(self.foreground)

self.pip1.setFill(self.foreground) self.pip4.setFill(self.foreground) self.pip7.setFill(self.foreground)

.

0

! 0

# #'

! @

self.pips[0].setFill(self.foreground) self.pips[3].setFill(self.foreground) self.pips[6].setFill(self.foreground)

Loop through pips and turn them all off Determine the list of pip indexes to turn on Loop through the list of indexes - turn on those pips 17

14

'

'

2

2

for pip in self.pips: self.pip.setFill(self.background) if value == 1: on = [3] elif value == 2: on = [0,6] elif value == 3: on = [0,3,6] elif value == 4: on = [0,2,4,6] elif value == 5: on = [0,2,3,4,6] else: on = [0,1,2,3,4,5,6] for i in on: self.pips[i].setFill(self.foreground)

. ! @ " # value& . 0 ! & . ' # # ) & : ) [0,3,6]

( ' !

1;

Python Programming, 1/e

8

#(& 5?

10

'

'

2
& p

0

'

! #

0 & & #key text #

# '

#

0

# #

"

for

) &

#

self.display.setText(text+key) 77

Python Programming, 1/e

74

13

D "

0

D try:

0

result = eval(text) except: result = 'ERROR‘ self.display.setText(str(result))

self.display.setText(“”)

"

0

0

# #

,) 8 !

self.display.setText(text[:-1])

"

* !

0

)

#

)

3

) '

3 ERROR

&

& #

&

7;

N 8

4?

*

D

!

8

#

" #

&

N

' *

!

# '

0

)

! !

' &

'

& '

! &

4

4

D " . # $ 3

# 0 ' ! $ %

D '

0 8! '

0# '

&

' 0

'

0

&

0

&

%& 0 8!

!

&

& 4(

Python Programming, 1/e

4+

14

D

D "

#

0 8! &

' )

0

>>> passwd = {"guido":"superprogrammer", "turing":"genius", "bill":"monopoly"}

W

0

!

!

'

V3 &

&

>>> passwd["guido"] 'superprogrammer' >>> passwd["bill"] 'monopoly'

[] '

! 0 &

41

45

D

D &" !

'

0

'

&

>>> passwd["bill"] = "bluescreen“ >>> passwd {'turing': 'genius', 'bill': 'bluescreen', 'guido': 'superprogrammer'}

0 0 # ' *

0 ! 0

' &

# #

#

@

3 ' &

-

A 47

44

D ! # ! W !

0

8

&

&

) #

%

$ '

& 8

#

>>> passwd['newuser'] = "ImANewbie“ >>> passwd {'turing': 'genius', 'bill': 'bluescreen', 'newuser': 'ImANewbie', 'guido': 'superprogrammer'}

&

4;

Python Programming, 1/e

;?

15

passwd = {} for line in open('passwords', 'r'): user, pass = string.split(line) passwd[user] = pass

' ' 0 8!

& ' # passwords # # '

' ' &

;

-

-

.has_key()

I

in

# # 0 # has_key

' &

.keys()

I

#

0 &

.values()

I

#

!

.items()

I

# (key, value) 0 8! &

.get(, )

&

key default

# '

del []

#

.clear()

!

M

&

&

;

>>> passwd.keys() ['turing', 'bill', 'newuser', 'guido'] >>> passwd.values() ['genius', 'bluescreen', 'ImANewbie', 'superprogrammer'] >>> passwd.items() [('turing', 'genius'), ('bill', 'bluescreen'), ('newuser', 'ImANewbie'), ('guido', 'superprogrammer')] >>> passwd.has_key('bill') True >>> 'fred' in passwd False >>> passwd.get('bill', 'unknown') 'bluescreen' >>> passwd.get('john', 'unknown') 'unknown' >>> passwd.clear() >>> passwd {}

;(

,) .

,) .

: *

N'

'

;+

!

: *

'

! 9

'

)

' &

"

. ' '

' )

! '

'

# #

#

$ 0

' & '3

.

%&

# ;1

Python Programming, 1/e

'

&

# # !

8 ' #

# @ ;5

16

,) .

,) .

: *

.

'

0

: *

" 3 ' counts& ) 0 KeyError&

' !

' & 23 counts& " # ' w counts[w] = counts[w] + 1 '

" # 3

'

8 8

if w is already in counts: add one to the count for w else: set count for w to 1

;7

,) .

;4

,) .

: *

" '

: *

# counts[w] = counts.get(w,0) + 1

' '

#w

#&

get ? # w

if counts.has_key(w): counts[w] = counts[w] + 1 else: counts[w] = 1

&

;;

,) .

,) .

: *

" #

0 *

. !

'

=

>

=

@ >

??

= '

> =

) #' )' $ ' % ! $ >%&

: *

fname = raw_input("File to analyze: ") # read file as one long string text = open(fname, 'r').read()

&

# convert all letters to lower case text = string.lower(text)

0

# replace each punctuation character with a space for ch in '!"#$%&()*+,-./:;?@[\\]^_{|}~': text = string.replace(text, ch, ' ') # split string at whitespace to form a list of words words = string.split(text) # Now we can easily loop through the words to build # the counts dictionary ?

Python Programming, 1/e

?

17

,) .

,) .

: *

: *

.

# get list of words that appear in document uniqueWords = counts.keys()

counts = {} for w in words: counts[w] = counts.get(w, 0) + 1

# put list of words in alphabetical order uniqueWords.sort()

. . c2: return -1 elif c1 == c2: return cmp(w1, w2) else: return 1

# ' 8 8 ? &

def compareItems((w1, c1), (w2, c2)): if c1 > c2: return -1 elif c1 == c2: return cmp(w1, w2) else: return 1

" # ' 8! #

0 &

' #

#

# '

?7

Python Programming, 1/e

?5

-1& ?4

18

.

: *

.

def compareItems((w1, c1), (w2, c2)): if c1 > c2: return -1 elif c1 == c2: return cmp(w1, w2) else: return 1

def compareItems((w1, c1), (w2, c2)): if c1 > c2: return -1 elif c1 == c2: return cmp(w1, w2) else: return 1

# '

' ' ! '

*

'

2

0 &"

3 '

: *

'

# 1&

"

&

items.sort(compareItems)

?;

.

: * &

import string

#8

.

def compareItems((w1,c1), (w2,c2)): if c1 > c2: return -1 elif c1 == c2: return cmp(w1, w2) else: return 1

# : N =

#

'

? 8

'3 >

: *

# wordfreq.py # Program to analyze the frequency of words in a text file. # Illustrates Python dictionaries

for i in range(n): print "%-10s%5d" % items[i]

N

?

.

" '

'

' ! GH

#

1 # ' !

def main(): print "This program analyzes word frequency in a file" print "and prints a report on the n most frequent words.\n"

&

: *

# get the sequence of words from the file fname = raw_input("File to analyze: ") text = open(fname,'r').read() text = string.lower(text) for ch in '!"#$%&\'()*+,-./:;?@[\\]^_`{|}~': text = string.replace(text, ch, ' ') words = string.split(text) # construct a dictionary of word counts counts = {} for w in words: counts[w] = counts.get(w,0) + 1 # output analysis of n most frequent words. n = input("Output analysis of how many words? ") items = counts.items() items.sort(compareItems) for i in range(n): print "%-10s%5d" % items[i] (

Python Programming, 1/e

19