# 1. del and index
# 2. len of a list
# 3. while loop : making a Celsius to Fahrenheit chart.
# 4. computing sin(x) = x - x^3/3! + x^5/5! ...
# 5. for loops and finishing the ctof program
# 6. Some more pretty printing

print "---------------------------"
print "Some more more lists"
print "---------------------------"

# 1. del and index
# Suppose you have a list
my_list = ['apple', 'banana', 'guava', 'chikoo']
print "New  print format : my_list =", my_list
print "Prev print format : my_list = %s" % my_list

# Deleting guava. Finding guava in the list.
n = my_list.index('guava')
print "Guava is in position", n, "."
# What happens when you search for something not in the list. The following
# two lines give ValueError
# n1 = my_list.index('papaya')
# print "Papaya is in position", n1, "."
# One can try
if 'papaya' in my_list :
	n1 = my_list.index('papaya')
	print "Papaya is in position", n1
else :
	print "Papaya is not in the list."

# To delete guava, you can just say
del my_list[my_list.index('guava')]
print "The list without guava is", my_list

# To delete papaya, which does not exist will cause errors; as you can see
# by running the following two lines
# del my_list[my_list.index('papaya')]
# print "The list without papaya is", my_list

if "papaya" in my_list :
	del my_list[my_list.index('papaya')]

print "After deleting papaya the list is :", my_list


# 2. len of a list

# The len function returns the length of the list
print "The number of fruits in the list is", len(my_list)
my_list.append('pineapple')
print "After adding pineapple, the number of fruits is", len(my_list),
print "and the fruits are", my_list, "."

# 3. while loop : making a Celsius to Fahrenheit chart.

# Back to loops. We shall do two problems, making a chart, and summing a
# series.

# Celsius to Fahrenheit conversion chart
print "C  F"
C = 0; F = 9.0/5 * C + 32; print C, F
C = 10; F = 9.0/5 * C + 32; print C, F
C = 20; F = 9.0/5 * C + 32; print C, F
C = 30; F = 9.0/5 * C + 32; print C, F

# This is boring. To facilitate repetitive statements we can use while using
# while statement
# Set starting point C = -40
# Set increment to be dC = 2
# Set C_max to be 60
# while C <= C_max do the following
# 	F = formula for fahrenheit in terms of C
#	print C and F
#	increase C by dC
# Once the loop completes halt the program

C = -40
dC = 2
C_max = 60
print "C\tF"
while C <= C_max :
	F = 9.0/5 * C + 32
	print C, "\t", F
	C = C + dC

# Exercise : Just to get your ideas clear, write a program to make a chart
# of Fahrenheit to Celsius conversion.

# Experiment with Boolean expressions. For an expression <exp> try running
# the following code to get an idea of what goes in the if and while
# statements.
# if <exp> :
# 	print "True"
# else :
# 	print "False"

# 4. computing sin(x) = x - x^3/3! + x^5/5! ...
# Let us use the while loop to do something more useful. The above sum is an
# infinite series. We cannot sum infinitely many summands on a computer. We
# however can sum a large number of summands. Let us denote the number of
# summands we want to consider by N.

import math # for the factorial funcion
k = 1 # k keeps track of which term we are adding. We start with the 1st
      # term. Note k varies over odd numbers.
N = 21 # Change it as you wish. Large values give more accurate results 
        # but take more computer time.

x = input("x : ")
x = float(x)
sign = 1
sinx = 0 # Name of the variable is sinx
while k <= N :
	sinx += sign * x**k / math.factorial(k) # stands for sinx = sinx + RHS
	sign = -sign
	k += 2 # similarly stands for k = k + 2
print "sin(%g) = %g. math libray gives the value %g." % (x, sinx, math.sin(x))

# 5. for loops and finishing the ctof program
# First create a list containing all the Celsius values we need to convert.
C_list = []
C_val = -40
C_incr = 2
C_max = 60
while C_val <= C_max :
	C_list.append(C_val)
	C_val += 2

print "The populated C_list is", C_list

print "23 in C_list : ", (23 in C_list)
print "24 in C_list : ", (24 in C_list)

print "C\tF"
for C in C_list :
	F = 9.0/5 * C + 32
	print C,"\t",F

# 6. Some more pretty printing
# Instead of the above, try the following :

for C in C_list :
	F = 9.0/5 * C + 32
	print "%5.1f C = %5.1f F" % (C, F)