dazcona

# Assume some existing list a, a list of strings.
# Determine whether a contains the string "blue".

a = ["red", "orange", "yellow",
     "green", "blue", "indigo", "violet"]

i = 0
while i < len(a) and a[i] != "blue":
   i = i + 1

dazcona

i = 0
while i < len(a):
   a[i] = a[i] + 1
   i = i + 1

dazcona

i = 0
while i < len(a):
   print a[len(a) - i - 1]
   i = i + 1

dazcona

a = ["red", "orange", "yellow",
     "green", "blue", "indigo", "violet"]

i = 0
while i < len(a):
   print a[i]
   i = i + 1

dazcona

a = ["red", "pink", "yellow",
     "green", "blue", "indigo", "violet"]

b = a

a[1] = "orange"

print a[1]  #      "orange"
print b[1]  # also "orange" !

dazcona

# Strings are immutable.
# Lists are mutable.
# "Immutable" means not able to change, and "mutable" means able to change.

# Given a string s, replace the character at position 4 with a "4".
s = "0123056789"
s = s[:4] + "4" + s[5:]
# Instead, we have to build a new string.

# This distinction is important: in Python, strings are immutable, we cannot change string values, we can, however, create a new string and assign that to s.

dazcona

# In literals:
# we use square brackets denote a list, and the elements are comma separated.

a = []                 # An empty list.
b = [1]
c = [3, 2, 1]
d = ["ab", "cd", "ef"]

a = ["red", "orange", "yellow",
     "green", "blue", "indigo", "violet"]

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# The syntax for accessing the individual elements of a list is the same as that for accessing the characters of a string.

s = "Mary had a little lamb."

print a[4]  # " "
print a[6]  # "a"

# The elements of a list can be values of any type.

a = [1, 1, 2, 3, 5, 8, 13, 21]

dazcona

s = raw_input()

# Test whether s[i] is a digit.
print "0" <= s[i] and s[i] <= "9"

# Test whether s[i] is not a digit.
print s[i] < "0" or "9" < s[i]

# Test whether s[i] is not a digit (alternative, possibly better).
print not ("0" <= s[i] and s[i] <= "9")

dazcona

#!/usr/bin/env python

n = input()

i = 2                                            # Linear search.
while i < n and n % i != 0:                      #
   i = i + 1                                     #

if n < 2 or i < n:
   print "not prime"