# introduction.py
'''
Gives a basic introduction into python.
'''

#
# Prelude
#
# Python code is interpreted.

# Python code runs on multiple platforms, given the right libraries are installed.

# Output
print("Hello World!")


#
# Variables
#
# Variables/Objects are not declared and typed dynamically.
a = 5
b = 7
c = a + b
d = "hello"

print(c)
print(hello)

# Variable names are case sensitive.
# Must start with _ or a letter, (not a number!)

A = 1
c = A + a
print(c)

a = True
b = False
print(a+b)
print(a*b)

# There are more binary operations, like XOR, etc.

# Types and conversion.
type(a)
float(a)


# Complex type.
(5j + 3) * (5j - 3)


# A few operators:
2+2
2-1
3*2
5/4 # integer division in Python 2.*
5./4 # float division in Python 2.*
5//4 # integer division
2**3 # power
5 % 4 # remainder of 5/4

# A few functions:
abs(a)
pow(a, b)
c = 5j + 3
c.conjugate()


#
# Strings
#
my_string = "chicken kidney pie"
print(my_string)
anotheshoer_string = 'beautiful blue raincoat'
print(another_string)

# Special characters and commands can be used using the backslash '\'
print('Don\'t worry,\nbe happy.')

# Some String operations.
print("It is a shoe! It is a shoe!\n" "It\'s a sandal!")

# String *slicing*.
my_string[0]
my_string[3]
my_string[-1]
my_string[2:4]
my_string[::2]

len(my_string)


#
# Functions.
#

# Functions return values and du something.
a = abs(-5)

# Get help (IPython):
abs?
abs??


#
# Try autocompletion with tab (IPython).
#


#
# Lists.
#
sequence = [1, 2, 5, 10, 20, 300]
sequence[0]
sequence[-1]
sequence[-2]
sequence[2:-3]

sequence + [1, 2]

sequence.append(500)
sequence[-1] = [-1, -2, -3]
sequence.append('what a twist!')

sequence.extend([1, 2])
# Find the first occurence of this element in the list.
sequence.index(1)
sequence.pop()
sequence.remove(1)
sequence.reverse()
sequence.sort()

#
# sets
#
# Sets are un-ordered collection of elements.

a = {0, 1, 4, 2, 1}

# Set operations:
b = set([0, 1, 3, 2, 2, 1])
a.intersection(b)
a.union(b)
a.issubset(b)
a - b
b - a


#
# Including libraries.
#

import numpy as np
import pylab as plt

np.pi
np.sin(3)


#
# Script files.
#

# Create a flie myScript.py.
# We can execude file using.

execfile('myScript.py')
# OR:
runfile('myScript.py')
# OR (Python 3):
exec(open("myScript.py").read())

# Or we can call it from the command line.
python myScript.py

# Comments can be added with the hash symbol.

# Identation matters!!!!!!
# Always 4 spaces!:


#
# Control Flow.
#

if x < 0:
    print("x is negative")
elif x == 0:
    print("x = 0")
else:
    print("x is positive")

# Boolean algebra.
if (x > 0) + (x < 0):
    print("x is not 0")
if (x > 0) or (x < 0):
    print("x is not 0")

if (x > 0) * (x < 1):
    print("x is in the open interval (0, 1)")
if (x > 0) and (x < 1):
    print("x is in the open interval (0, 1)")

# Loops
my_list = [0, 1, 2, 3]
for i in my_list:
    print(i)

my_list = [10, 20, 3, 4]
for i, j in enumerate(my_list):
    print(i, j)

for i in range(10):
    print(i)

for i in range(5, 10):
    print(i)

for i in range(10):
    print(i)
    if i == 5:
        break

for i in range(10):
    if i == 5:
        continue
    print(i)

i = 0
while i < 5:
    print(i)
    i += 1

# Do nothing.
if a > 0:
    print("a is positive")
else:
    pass

# Python requires at least one command in command blocks.