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Arevos · Jan 5th, 2007, 5:04 AM

Loops are used for repeating blocks of code. There are two basic types of loops; while loops, which keep repeating until a condition is met, and for loops, which repeat for each item in a list.

Here's an example of a "while" loop:

 python Syntax (Toggle Plain Text) 
from datetime import datetime
 
while user_input != "q":
    print "The date and time is %s" % datetime.now()
 
    print "Type in 'q' to quit, or press enter to print the date again."
 
    user_input = raw_input()
from datetime import datetime

while user_input != "q":
    print "The date and time is %s" % datetime.now()

    print "Type in 'q' to quit, or press enter to print the date again."

    user_input = raw_input()

The while loop will keep repeating the date and time until the user types in "q".

And here's an example of a "for" loop:

 python Syntax (Toggle Plain Text) 
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
 
print "The 7 times table: "
 
for number in numbers:
    print "%d times 7 is %d" % (number, number * 7)
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

print "The 7 times table: "

for number in numbers:
    print "%d times 7 is %d" % (number, number * 7)

The for loop will output the 7 times table, without you having to type every line. You can also use the "range" function to return a list of numbers:

 python Syntax (Toggle Plain Text) 
>>> range(10)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> range(1, 10)
[1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> range(1, 11)
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> range(10)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> range(1, 10)
[1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> range(1, 11)
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

When given one number N, the sequence range returns is 0 <= x < N. When given two numbers N and M, the range is N <= x < M.

It's a little counter intuitive, but there are a few good reasons for not including the last number.

Jan 5th, 2007, 5:04 AM	#30
Arevos Programming Guru Join Date: Aug 2005 Location: England Posts: 1,499 Rep Power: 5	Loops are used for repeating blocks of code. There are two basic types of loops; while loops, which keep repeating until a condition is met, and for loops, which repeat for each item in a list. Here's an example of a "while" loop: python Syntax (Toggle Plain Text) from datetime import datetime while user_input != "q": print "The date and time is %s" % datetime.now() print "Type in 'q' to quit, or press enter to print the date again." user_input = raw_input() from datetime import datetime while user_input != "q": print "The date and time is %s" % datetime.now() print "Type in 'q' to quit, or press enter to print the date again." user_input = raw_input() The while loop will keep repeating the date and time until the user types in "q". And here's an example of a "for" loop: python Syntax (Toggle Plain Text) numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] print "The 7 times table: " for number in numbers: print "%d times 7 is %d" % (number, number * 7) numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] print "The 7 times table: " for number in numbers: print "%d times 7 is %d" % (number, number * 7) The for loop will output the 7 times table, without you having to type every line. You can also use the "range" function to return a list of numbers: python Syntax (Toggle Plain Text) >>> range(10) [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] >>> range(1, 10) [1, 2, 3, 4, 5, 6, 7, 8, 9] >>> range(1, 11) [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] >>> range(10) [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] >>> range(1, 10) [1, 2, 3, 4, 5, 6, 7, 8, 9] >>> range(1, 11) [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] When given one number N, the sequence range returns is 0 <= x < N. When given two numbers N and M, the range is N <= x < M. It's a little counter intuitive, but there are a few good reasons for not including the last number.