1. Concept of a collection

• A collection allows us to put many values in a single “variable”
• A collection is nice because we can carry all many values around in one convenient package.

friends = [ 'Joseph', 'Glenn', 'Sally' ]

carryon = [ 'socks', 'shirt', 'perfume' ]

• What is not a “Collection”
  • Most of our variables have one value in them - when we put a new value in the variable - the old value is over written

$ python
Python 2.5.2 (r252:60911, Feb 22 2008, 07:57:53)
[GCC 4.0.1 (Apple Computer, Inc. build 5363)] on darwin
>>> x = 2
>>> x = 4
>>> print x
4

2. Lists and definite loops

• List constants are surrounded by square brackets and the elements in the list are separated by commas.
• A list element can be any Python object - even another list
• A list can be empty

>>> print [1, 24, 76]
[1, 24, 76]
>>> print ['red', 'yellow', 'blue']
['red', 'yellow', 'blue']
>>> print ['red', 24, 98.6]
['red', 24, 98.599999999999994]
>>> print [ 1, [5, 6], 7]
[1, [5, 6], 7]
>>> print []
[]

3. Indexing and lookup

friends = ['Joseph', 'Glenn', 'Sally']
for friend in friends :
    print 'Happy New Year:',  friend
print 'Done!'

Happy New Year: Joseph
Happy New Year: Glenn
Happy New Year: SallyDone!

• Just like strings, we can get at any single element in a list using an index specified in square brackets

>>> friends = [ 'Joseph', 'Glenn', 'Sally' ]
>>> print friends[1]
Glenn
>>>

4. List mutability

• Strings are “immutable” - we cannot change the contents of a string - we must make a new string to make any change
• Lists are “mutable” - we can change an element of a list using the index operator

>>> fruit = 'Banana’
>>> fruit[0] = 'b’
Traceback
TypeError: 'str' object does not
support item assignment
>>> x = fruit.lower()
>>> print x
banana
>>> lotto = [2, 14, 26, 41, 63]
>>> print lotto[2, 14, 26, 41, 63]
>>> lotto[2] = 28
>>> print lotto
[2, 14, 28, 41, 63]

5. Functions: len, min, max, sum

• The len() function takes a list as a parameter and returns the number of elements in the list
• Actually len() tells us the number of elements of any set or sequence (i.e. such as a string…)

>>> greet = 'Hello Bob'
>>> print len(greet)
9
>>> x = [ 1, 2, 'joe', 99]
>>> print len(x)
4
>>>

6. Slicing lists

7. List methods: append, remove

8. Sorting lists

9. Splitting strings into lists of words

10. Using split to parse strings

Week7 Files

1.Secondary storage

2.Opening a file - file handle

1. Before we can read the contents of the file we must tell Python which file we are going to work with and what we will be doing with the file
2. This is done with the open() function
3. open() returns a “file handle” - a variable used to perform operations on the file
4. Kind of like “File -> Open” in a Word Processor

2.1 Using open()

handle = open(filename, mode)

fhand = open('mbox.txt', 'r')

1. returns a handle use to manipulate the file
2. filename is a string
3. mode is optional and should be ‘r’ if we are planning reading the file and ‘w’ if we are going to write to the file.

>>> fhand = open('mbox.txt')
>>> print fhand
<open file 'mbox.txt', mode 'r' at 0x1005088b0>\

2.3 When files are missing

>>> fhand = open('stuff.txt')
Traceback (most recent call last):  File "<stdin>", line 1, in <module>IOError: [Errno 2] No such file or directory: 'stuff.txt'

3.File structure - newline character

1. We use a special character to indicate when a line ends called the “newline”
2. We represent it as \n in strings
3. Newline is still one character - not two

>>> stuff = 'Hello\nWorld!’
>>> stuff'Hello\nWorld!’
>>> print stuff
HelloWorld!
>>> stuff = 'X\nY’
>>> print stuff
X
Y
>>> len(stuff)3

4.Reading a file line-by-line with a for loop

1. A file handle open for read can be treated as a sequence of strings where each line in the file is a string in the sequence
2. We can use the for statement to iterate through a sequence
3. Remember - a sequence is an ordered set

xfile = open('mbox.txt')
for cheese in xfile:
    print cheese

4.1 Counting Lines in a File

1. Open a file read-only
2. Use a for loop to read each line
3. Count the lines and print out the number of lines

fhand = open('mbox.txt')
count = 0
for line in fhand:
     count = count + 1
print 'Line Count:', count

$ python open.py
Line Count: 132045

4.2 Reading the Whole File

We can read the whole file (newlines and all) into a single string.

>>> fhand = open('mbox-short.txt')
>>> inp = fhand.read()
>>> print len(inp)94626
>>> print inp[:20]From stephen.marquar

5.Searching for lines

5.1 using if to select

We can put an if statement in our for loop to only print lines that meet some criteria

fhand = open('mbox-short.txt')
for line in fhand:
      if line.startswith('From:') :
            print line
            
            
From: stephen.marquard@uct.ac.za

From: louis@media.berkeley.edu

From: zqian@umich.edu

From: rjlowe@iupui.edu

            

Each line from the file has a newline at the end.
The print statement adds a newline to each line.

From: stephen.marquard@uct.ac.za\n
\n
From: louis@media.berkeley.edu\n
\n
From: zqian@umich.edu\n
\n
From: rjlowe@iupui.edu\n
\n

• We can strip the whitespace from the right hand side of the string using rstrip() from the string library
• The newline is considered “white space” and is stripped

fhand = open('mbox-short.txt')
for line in fhand:
      line = line.rstrip()
      if line.startswith('From:') :            
      
      
From: stephen.marquard@uct.ac.za
From: louis@media.berkeley.edu
From: zqian@umich.edu
From: rjlowe@iupui.edu

5.2 Skipping with continue

We can convienently skip a line by using the continue statement

fhand = open('mbox-short.txt')
for line in fhand:
    line = line.rstrip()
    if not line.startswith('From:') :
        continue
    print line

5.3 Using in to select lines

• We can look for a string anywhere in a line as our selection criteria

fhand = open('mbox-short.txt')
for line in fhand:
    line = line.rstrip()
    if not '@uct.ac.za' in line : 
        continue
    print line

6.Reading file names

Prompt for File Name

fname = raw_input('Enter the file name:  ')
fhand = open(fname)
count = 0
for line in fhand:
    if line.startswith('Subject:') :
        count = count + 1
print 'There were', count, 'subject lines in', fname

Enter the file name:  mbox.txt
There were 1797 subject lines in mbox.txt

Enter the file name: mbox-short.txt
There were 27 subject lines in mbox-short.txt

7.Dealing with bad files

fname = raw_input('Enter the file name:  ')
try:
    fhand = open(fname)
except:
    print 'File cannot be opened:', fname
    exit()
count = 0
for line in fhand:
    if line.startswith('Subject:') :
        count = count + 1
print 'There were', count, 'subject lines in', fname

Enter the file name: mbox.txt
There were 1797 subject lines in mbox.txt

Enter the file name: na na boo boo
File cannot be opened: na na boo boo

Week 6 Strings

1.String type

• A string is a sequence of characters
• A string literal uses quotes ‘Hello’ or “Hello”
• For strings, + means “concatenate”
• When a string contains numbers, it is still a string
• We can convert numbers in a string into a number using int()

>>> str1 = "Hello"
>>> str2 = 'there'
>>> bob = str1 + str2
>>> print bob
Hellothere
>>> str3 = '123'
>>> str3 = str3 + 1
Traceback (most recent call last):  File "<stdin>", line 1, in <module>TypeError: cannot concatenate 'str' and 'int' objects
>>> x = int(str3) + 1
>>> print x
124
>>> 

2.Read/Convert

• We prefer to read data in using strings and then parse and convert the data as we need
• This gives us more control over error situations and/or bad user input
• Raw input numbers must be converted from strings

>>> name = raw_input('Enter:')
Enter:Chuck
>>> print name
Chuck
>>> apple = raw_input('Enter:')
Enter:100
>>> x = apple – 10
Traceback (most recent call last):  File "<stdin>", line 1, in <module>TypeError: unsupported operand type(s) for -: 'str' and 'int'
>>> x = int(apple) – 10
>>> print x
90

3.Indexing strings []

• We can get at any single character in a string using an index specified in square brackets
• The index value must be an integer and starts at zero
• The index value can be an expression that is computed

>>> fruit = 'banana'
>>> letter = fruit[1]
>>> print letter
a
>>> n = 3
>>> w = fruit[n - 1]
>>> print w
n

• You will get a python error if you attempt to index beyond the end of a string.
• So be careful when constructing index values and slices

>>> zot = 'abc'
>>> print zot[5]
Traceback (most recent call last):  File "<stdin>", line 1, in <module>IndexError: string index out of range
>>> 

3.1 length of strings

There is a built-in function len that gives us the length of a string

>>> fruit = 'banana'
>>> print len(fruit)
6

>>> fruit = 'banana'
>>> x = len(fruit)
>>> print x
6

A function is some stored code that we use. A function takes some input and produces an output.

4.Slicing strings [2:4]

• We can also look at any continuous section of a string using a colon operator
• The second number is one beyond the end of the slice - “up to but not including”
• If the second number is beyond the end of the string, it stops at the end

>>> s = 'Monty Python'
>>> print s[0:4]
Mont
>>> print s[6:7]
P
>>> print s[6:20]
Python

• If we leave off the first number or the last number of the slice, it is assumed to be the beginning or end of the string respectively

>>> s = 'Monty Python'
>>> print s[:2]
Mo
>>> print s[8:]
Thon
>>> print s[:]
Monty Python

5.Looping through strings with for and while

• Using a while statement and an iteration variable, and the len function, we can construct a loop to look at each of the letters in a string individually

fruit = 'banana'
index = 0
while index < len(fruit) : 
   letter = fruit[index]
    print index, letter
    index = index + 1

0 b
1 a
2 n
3 a
4 n
5 a

• A definite loop using a for statement is much more elegant
  The iteration variable is completely taken care of by the for loop

fruit = 'banana'
for letter in fruit : 
   print letter

b
a
n
a
n
a

• This is a simple loop that loops through each letter in a string and counts the number of times the loop encounters the ‘a’ character.

word = 'banana'
count = 0
for letter in word :
    if letter == 'a' : 
       count = count + 1
print count

• The iteration variable “iterates” through the sequence (ordered set)
• The block (body) of code is executed once for each value in the sequence
• The iteration variable moves through all of the values in the sequence

6.Concatenating strings with +

• When the + operator is applied to strings, it means “concatenation”

>>> a = 'Hello'
>>> b = a + 'There'
>>> print b
HelloThere
>>> c = a + '  ' + 'There'
>>> print c
Hello There
>>> 

7.String operations

• Python has a number of string functions which are in the string library
• These functions are already built into every string - we invoke them by appending the function to the string variable
• These functions do not modify the original string, instead they return a new string that has been altered

>>> stuff = 'Hello world’
>>> type(stuff)<type 'str'>
>>> dir(stuff)
['capitalize', 'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']

7.1 String Comparison

if word == 'banana':
    print  'All right, bananas.'

if word < 'banana':
    print 'Your word,' + word + ', comes before banana.’
elif word > 'banana':
    print 'Your word,' + word + ', comes after banana.’
else:
    print 'All right, bananas.'

7.2 Searching a String

• We use the find() function to search for a substring within another string
• find() finds the first occurance of the substring
  If the substring is not found, find() returns -1
  Remember that string position starts at zero

>>> fruit = 'banana'
>>> pos = fruit.find('na')
>>> print pos
2
>>> aa = fruit.find('z')
>>> print aa
-1

7.3 Making everything UPPER CASE

• You can make a copy of a string in lower case or upper case
• Often when we are searching for a string using find()- we first convert the string to lower case so we can search a string regardless of case

>>> greet = 'Hello Bob'
>>> nnn = greet.upper()
>>> print nnn
HELLO BOB
>>> www = greet.lower()
>>> print www
hello bob
>>> 

7.4 Search and Replace

• The replace() function is like a “search and replace” operation in a word processor
• It replaces all occurrences of the search string with the replacement string

>>> greet = 'Hello Bob'
>>> nstr = greet.replace('Bob','Jane')
>>> print nstr
Hello Jane
>>> nstr = greet.replace('o','X')
>>> print nstrHellX BXb
>>> 

7.5 Stripping Whitespace

• Sometimes we want to take a string and remove whitespace at the beginning and/or end
• lstrip() and rstrip() to the left and right only
• strip() Removes both begin and ending whitespace

>>> greet = '   Hello Bob  '
>>> greet.lstrip()
'Hello Bob  '
>>> greet.rstrip()
'   Hello Bob'
>>> greet.strip()
'Hello Bob'
>>> 

7.6 Prefixes

>>> line = 'Please have a nice day’
>>> line.startswith('Please')
True
>>> line.startswith('p')
False

7.7 Parsing and Extracting

From stephen.marquard@uct.ac.za Sat Jan 5 09:14:16 2008

>>> data = 'From stephen.marquard@uct.ac.za Sat Jan  5 09:14:16 2008’
>>> atpos = data.find('@')
>>> print atpos
21
>>> sppos = data.find(' ',atpos)
>>> print sppos
31
>>> host = data[atpos+1 : sppos]
>>> print host
uct.ac.za

Week 5 Loops and iterations

1. While loops (indefinite)

Loops (repeated steps) have iteration variables that change each time through a loop. Often these iteration

While loops are called “indefinite loops” because they keep going until a logical condition becomes False

n = 5
while n > 0 :
    print n
    n = n – 1
print 'Blastoff!'
print n

2. Infinite loops

n = 5
while n > 0 :
    print 'Lather’
    print 'Rinse'
print 'Dry off!'

3. Using break

• The break statement ends the current loop and jumps to the statement immediately following the loop
• It is like a loop test that can happen anywhere in the body of the loop

while True:
    line = raw_input('> ')
    if line == 'done' :
        break
    print line
print 'Done!'

> hello there
hello there
> finished
finished
> done
Done!

4. Using continue

The continue statement ends the current iteration and jumps to the top of the loop and starts the next iteration

while True:
    line = raw_input('> ')
    if line[0] == '#' :
        continue
    if line == 'done' 
:        break
    print line
print 'Done!'

> hello there
hello there
> # don't print this
> print this!
print this!
> done
Done!

5. For loops (definite)

• Quite often we have a list of items of the lines in a file effectively a finite set of things
• We can write a loop to run the loop once for each of the items in a set using the Python for construct
• These loops are called “definite loops” because they execute an exact number of times
• We say that “definite loops iterate through the members of a set”

friends = ['Joseph', 'Glenn', 'Sally']
for friend in friends : 
   print 'Happy New Year:',  friend
print 'Done!'

Happy New Year: Joseph
Happy New Year: Glenn
Happy New Year: Sally
Done!

6. Iteration variables

• The iteration variable “iterates” though the sequence (ordered set)
• The block (body) of code is executed once for each value in the sequence
• The iteration variable moves through all of the values in the sequence

6.1 Counting in a Loop

zork = 0
print 'Before', zork
for thing in [9, 41, 12, 3, 74, 15] :
    zork = zork + 1
    print zork, thing
print 'After', zork

#To count how many times we execute a loop we introduce a counter variable that starts at 0 and we add one to it each time through the loop.

$ python countloop.py
Before 0
1 9
2 41
3 12
4 3
5 74
6 15
After 6

6.2 Summing in a Loop

zork = 0
print 'Before', zork
for thing in [9, 41, 12, 3, 74, 15] :
    zork = zork + thing
    print zork, thing
print 'After', zork

#To add up a value we encounter in a loop,  we introduce a sum variable that starts at 0 and we add the value to the sum each time through the loop.

$ python countloop.py 
Before 0
9 9
50 41
62 12
65 3
139 74
154 15
After 154

6.3 Finding the Average in a Loop

count = 0
sum = 0
print 'Before', count, sum
for value in [9, 41, 12, 3, 74, 15] :
    count = count + 1
    sum = sum + value
    print count, sum, value
print 'After', count, sum, sum / count

#An average just combines the counting and sum patterns and divides when the loop is done.

$ python averageloop.py 
Before 0 0
1 9 9
2 50 41
3 62 12
4 65 3
5 139 74
6 154 15
After 6 154 25

6.4 Filtering in a Loop

print 'Before'
for value in [9, 41, 12, 3, 74, 15] :
    if value > 20:
 	    print 'Large number',value
print 'After'

# We use an if statement in the loop to catch / filter the values we are looking for.

$ python search1.py 
Before
Large number 41
Large number 74
After

6.5 Search Using a Boolean Variable

found = False
print 'Before', found
for value in [9, 41, 12, 3, 74, 15] : 
   if value == 3 :
         found = True
    print found, value
print 'After', found

#If we just want to search and know if a value was found - we use a variable that starts at False and is set to True as soon as we find what we are looking for.

$ python search1.py 
Before False
False 9
False 41
False 12
True 3
True 74
True 15
After True

7. Largest or smallest

smallest = None #特殊类型变量
print 'Before'
for value in [9, 41, 12, 3, 74, 15] :
    if smallest is None : #IS是逻辑运算符，少用 主要是为了检查是否是 none 或 false
        smallest = value
    elif value < smallest : 
        smallest = value
    print smallest, value
print 'After', smallest

# We still have a variable that is the smallest so far.  The first time through the loop smallest is None so we take the first value to be the smallest.

    $ python smallest.py 
    Before
    9 9
    9 41
    9 12
    3 3
    3 74
    3 15
    After 3

Week 4 Functions

1.Stored (and reused) Steps

def hello(): #定义函数(store)
    print 'Hello'
    print 'Fun'
    
hello() #调用函数(reuse)
print 'Zip'
hello() #调用函数(reuse)

Type Conversion
Built in functions int() and float()

2.Python Functions

2.1. Built in functions that are provided

-input: raw_input()
-type conversions: type()
-string conversions: str() int()

2.2. Defined functions

-arguments as input
-def to define

big= max('Hello world') #定义函数 不会执行
print big #调用函数 执行

Names of built in function == New reserved words

3.Arguments

• is a value pass into the function
• need to be in the ()

3.1 Parameters

A parameter is a variable which we use in the functions

definition that is a “handle” that allows the code in the function to access the arguments for a particular function invocation.

        def greet(lang):
            if lang == 'es':
               print 'Hola’
            elif lang == 'fr':
               print 'Bonjour’
            else:
               print 'Hello’
    greet('en')Hello
    greet('es')Hola
    greet('fr')Bonjour

3.2 Return Values

Often a function will take its arguments, do some computation and return a value to be used as the value of the function call in the calling expression. The return keyword is used for this.

>>> def greet(lang):
...         if lang == 'es':
...            return 'Hola’
...         elif lang == 'fr':
...            return 'Bonjour’
...         else:
...            return 'Hello’
... >>> print greet('en'),'Glenn’
Hello Glenn
>>> print greet('es'),'Sally’
Hola Sally
>>> print greet('fr'),'Michael’
Bonjour Michael
>>> 

Week 3 Conditional execution

1. Conditional Steps

st=>start: x=5
e=>end: print 'finis'
cond1=>condition: x<10?
op1=>operation: print 'Smaller'
cond2=>condition: x>20?
op2=>operation: print 'Bigger'
st->cond1->cond2
cond1(yes)->op1->e
cond1(no)->cond2
cond2(yes)->op2->e
cond2(no)->e

2. Comparison Operators

<     less than
<=	  less than or equal
==    equal to
>=    greater than or equal
>     greater than 
!=    not equal

1. Boolean expressions ask a question and produce a Yes or No result which we use to control program flow
2. Boolean expressions using comparison operators evaluate to - True / False - Yes / No
3. Comparison operators look at variables but do not change the variables

3. Logical operators: and or not

4. Indentation

Indentation DO matter in python.

1. Increase indent after an if statement or for statement (after : )
2. Maintain indent to indicate the scope of the block (which lines are affected by the if/for)
3. Reduce indent to back to the level of the if statement or for statement to indicate the end of the block
4. Blank lines are ignored - they do not affect indentation
5. Comments on a line by themselves are ignored

   Warning: Turn Off Tabs
   Or change the editor setting

5. One Way Decisions

5.1 流程图如下

st=>start: x=5
e=>end: print 'Afterwards 5'
cond1=>condition: x==5?
op1=>operation: print 'is 5'
op2=>operation: print 'Still 5'
op3=>operation: print 'Third 5'
op4=>operation: print 'Before 5'
st->op4->cond1->e
cond1(yes)->op1->op2->op3->e
cond1(no)->e

5.2 代码如下：

    x = 5
	print 'Before 5’
	if  x == 5 :
	    print 'Is 5’
	    print 'Is Still 5’
	    print 'Third 5’
	print 'Afterwards 5’

5.3 显示结果如下：

    Before 5
	Is 5
	Is Still 5
	Third 5
	Afterwards 5

6. Two way Decisions if : and else :

6.1 流程图如下：

st=>start: x=4
e=>end: print 'All Done'
op1=>operation: print 'Smaller'
op2=>operation: print 'Bigger'
cond1=>condition: x>2
st->cond1
cond1(yes)->op2->e
cond1(no)->op1->e

6.2 代码如下：

    x=4
    if x>2:
	    print 'Bigger'
	else:
		print 'Smaller'
	print 'All Done'

7. Nested Decisions(嵌套)

7.1 流程图如下：

st=>start: start
e=>end: end
cond1=>condition: x>1
cond2=>condition: x<100
op1=>operation: print 'More than one'
op2=>operation: print 'Less than 100'
op2=>operation: print 'All Done'
st->cond1->e
cond1(no)->e
cond1(yes)->op1->cond2
cond2(yes)->op2->e
cond2(no)->e

7.2 代码如下：

    x = 42

	if x > 1 :
	    print 'More than one'
	    if x < 100 : 
	        print 'Less than 100'

	print 'All done'

8. Multiway decisions using elif

8.1 流程图如下:

st=>start: start
cond1=>condition: x<2
cond2=>condition: x<10
cond3=>condition: x<20
cond4=>condition: x<40
cond5=>condition: x<100
op1=>operation: print 'Small'
op2=>operation: print 'Medium'
op3=>operation: print 'Big'
op4=>operation: print 'Large'
op5=>operation: print 'Huge'
op6=>operation: print 'Ginormous'
st->cond1
cond1(yes)->op1
cond2(yes)->op2
cond3(yes)->op3
cond4(yes)->op4
cond5(yes)->op5
cond1(no)->cond2
cond2(no)->cond3
cond3(no)->cond4
cond4(no)->cond5
cond5(no)->op6->e

8.2代码如下：

    if x < 2 :
	    print 'Small'
	elif x < 10 :
	    print 'Medium'
	elif x < 20 : 
	    print 'Big'
	elif x< 40 : 
	    print 'Large'
	elif x < 100:
	    print 'Huge'
	else :
    print 'Ginormous'

8.3 Multi-way Puzzles-Which will never print?

if x < 2 :
    print 'Below 2'
elif x >= 2 : 
    print 'Two or more'
**else : #此行之后不执行
    print 'Something else'** 

if x < 2 :
    print 'Below 2'
elif x < 20 :
    print 'Below 20'
**elif x < 10 :  #以下两行不执行
    print 'Below 10'**
else :
    print 'Something else'

9. Try / Except to compensate for errors

1. You surround a dangerous section of code with try and except.
2. If the code in the try works - the except is skipped
3. If the code in the try fails - it jumps to the except section

9.1 示例代码如下：

rawstr = raw_input('Enter a number:')
try: 
    ival = int(rawstr)
except: 
    ival = -1

if ival > 0 :  
    print 'Nice work'else:  
    print 'Not a number'

10. Exercise

10.1 Exercise 3.1

Rewrite your pay computation to give the employee 1.5 times the hourly rate for hours worked above40 hours.

hours=raw_input("How many hours do you work per week?\n")
try: 
    Hours = float(hours)
    rate=raw_input("How much do you get paid per hour?\n")
    try: 
        Rate = float(rate)
        if Hours < 40 :
            TotalPay=float(Hours)* float(Rate)
            print "So, you get paid " + str(TotalPay) + " per week?" 
        else:
            TotalPay=(float(Hours)-40)*1.5*float(Rate)+40*float(Rate)
            print "So, you get paid " + str(TotalPay) + " dollars per week?"
    except: 
        Rate = -1
    if Rate <0 :
        print "Please enter numeric input!"
except: 
    Hours = -1
if Hours <0 :
    print "Please enter numeric input!"

10.2 Exercise 3.3

Write a program to prompt for a score between 0.0 and 1.0. If the score is out of range print an error. If the score is between 0.0 and 1.0, print a grade using the following table:

score=raw_input("Please input the score!\n")
try:
    Score = float(score)
    if Score < 0.6 :
        print "Your Grade is F!"
    elif Score < 0.7 :
        print "Your Grade is D!"
    elif Score < 0.8 :
        print "Your Grade is C!"
    elif Score < 0.9 :
        print "Your Grade is B!"
    elif Score < 1.0 :
        print "Your Grade is A!"
    else :
        print "Please enter the right score!"
except:
    Score = -1
if Score < 0 :
    print "Error, please enter numeric input!"

Week 2 expressions

1. Values and types

15. Exercises

Exercises 2.2

Write a program that uses raw_input to prompt a user for their name and then welcomes them.

Name=raw_input('Hi! What is your name?\n')
print 'Hello '+ Name + ', welcome to the new world !'

2.3 Write a program to prompt the user for hours and rate per hour to compute gross pay

Hours=raw_input("How many hours do you work per day?\n")
Rate=raw_input("How much do you get paid for an hours?\n")
TotalHours=float(Hours)* float(Rate)
print "So, you work " + str(TotalHours) + " hours per week?"

2.5 Write a program to prompt the user for a Celsius temperature, convert the temperature to Fahrenheit and print out the converted temperature.

Ctemp=raw_input("Please enter the Celsius temperature:\n")
Ftemp=(int(Ctemp)*9/5)+32
print str(Ctemp) + ' degree celsius is ' + str(Ftemp) + ' degree fahrenheit!\n '