1) Operators for Numbers

 a = b Assign b to a a = 1 + 2 Add 1 and 2 and store in a a = 3 - 4 Subtract 4 from 3 and store in a a = a + b Add a and b; store in a a = 5 * 6 Multiply 5 and 6 a = 7.0 / 8.0 Divide 7 by 8, yields 0.875 a = 7 / 8 Divide 7 by 8, yields 0 a = 9.0 ** 10 9 to the power of 10 a = 5 % 2 Remainder of 5 divided by 2 int(a) converts string into number

Exercise: Operating with Numbers

#!/usr/bin/env python
#
# This program converts from US \$ to Canadian \$

us_money = input ("Money value in US \$ ")

can_money = us_money /0.6
print "US\$", us_money, "= Canandian \$", can_money

1.1) In analogy to the example, write a script that asks users for the temperature in F and prints the temperature in C. (Conversion: Celsius = (F - 32) * 5/9 )

2) Strings

A string is delimited by double quotes ("..."). Certain special characters can be used, such as "\n" (for newline) and "\t" (for a tab). To print the characters " and \, they must be preceded by a backslash (\). A \ at end of line is used to continue a string on the next line. A multi-line print statement should be enclosed by three double quotes ("""...""").

#!/usr/bin/env python
#
print "hello\n"
print "To print a newline use \\n"
print "She said: \"hello\""
print "\tThis is indented"
print "This is a very, very, very, very, very, very \
long print statment"
print """
This is a multi-line print statement
First line
Second line
"""

Exercise:

2.1) Write a python script that prints the following figure

```       \  |  /
@ @
*
\"""/
```

3) Operators and functions for strings

 a = b + c concatenate b and c a = b * c b repeated c times a the first character of a len(a) the number of characters in a min(a) the smallest element in a (alphabetically first) max(a) the largest element in a (alphabetically last)

Example:

#!/usr/bin/env python
#
# String operations

b = "the"
c = "cat"
d = " is on the mat"
a = b + " " + c + d
print a
b = b + " "
a = b * 5
print a
print "The first character of", c, "is" ,c
print "The word \""+ c+ "\" has", len(c) ,"characters"

name = (name + "!") * 5
print name

Exercise:

3.1) Write a program that asks users for their favourite color. Create the following output (assuming "red" is the chosen color). Use "+" and "*".

```red red red red red red red red red red
red                                 red
red                                 red
red red red red red red red red red red
```

4) Control structures: if

This is just a first introduction to control structures. They will be covered in more detail during the next two weeks.

#!/usr/bin/env python
# if statement

answer = raw_input("Do you like Python? ")