Python: Difference between revisions

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Line 116: Line 116:
  months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']
  months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']
   if 1 <= which_one <= 12:
   if 1 <= which_one <= 12:
  print "The month is", months[which_one - 1]
  print "The month is", months[which_one - 1]

Revision as of 18:58, 10 October 2011

links

http://en.wikibooks.org/wiki/Non-Programmer%27s_Tutorial_for_Python_2.6
http://docs.python.org/tutorial

Reference

http://docs.python.org/ref/ref.html

basics

print "Hello, World!"

command called print followed by one argument,which is "Hello, World!". (referred to as a string of characters, or string) Command and its arguments are collectively referred to as a statement,

print "2 + 2 is", 2 + 2

The first argument is the string "2 + 2 is" and the second argument is the mathematical expression 2 + 2, which is commonly referred to as an expression. each of the arguments separated by a comma

sys.argv   arguments are passed to the script in the variable sys.argv
#          is used to start a comment

operations for numbers

Operation Symbol Example
Power (exponentiation) ** 5 ** 2 == 25
Multiplication * 2 * 3 == 6
Division / 14 / 3 == 4
Remainder (modulo) % 14 % 3 == 2
Addition + 1 + 2 == 3
Subtraction - 4 - 3 == 1

userinput

raw_input (returns a string)

user_reply = raw_input("Who goes there? ")

input (returns digits)

number = input("Type in a number: ")

type(number) (tells what a variable is.)

print "number is a", type(number)

while loop

print number interval. finish while loop with a ':' The while statement only affects the lines that are indented with whitespace.

start = input("Start number? ")
stop = input("Stop number? ")
a = start
while a < stop:
    print a
    a = a + 1
operator function
< less than
<= less than or equal to
> greater than
>= greater than or equal to
== equal
!= not equal
<> another way to say not equal (old style, not recommended)

if statment

 if a > 5:  
   print a, ">", 5
 elif a <= 7:
   print a, "<=", 7
 else:
   print "Neither test was true"
  1. This Program Demonstrates the use of the == operator # using numbers
print 5 == 6 

false

functions

The key feature of this program is the def statement. def (short for define) starts a function definition. def is followed by the name of the function absolute_value. Next comes a '(' followed by the parameter n (n is passed from the program into the function when the function is called). The statements after the ':' are executed when the function is used. The statements continue until either the indented statements end or a return is encountered. The return statement returns a value back to the place where the function was called.

def absolute_value(n):
  if n < 0:
    n = -n
  return n

import

Sleep

import time
time.sleep(secs)

random

import random
number = random.randrange(1, 100, 1)

list

list with more than one value.

which_one = input("What month (1-12)? ")
months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']
 if 1 <= which_one <= 12:
print "The month is", months[which_one - 1]