#!/usr/bin/env python
# coding: utf-8

# <span style="font-size: 200%">Introduction to Python (3)</span>
# ===

# Functions
# ===
# 
# A _function_ is a named sequence of statements that performs some piece of work.
# Later on that function can be called by using its name.
# 
# Defining a function
# ---
# 
# A function definition includes its _name_, _arguments_ and _body_.

# In[1]:


def add_two(number):
    return number + 2


# In[2]:


for i in range(5):
    print add_two(i)


# Functions
# ===
# 
# Keyword arguments
# ---
# 
# Besides regular arguments, functions can have keyword arguments.

# In[3]:


def add_some_other_number(number, other_number=12):
    return number + other_number


# In[4]:


add_some_other_number(2, 6)


# In[5]:


add_some_other_number(3, other_number=4)


# In[6]:


add_some_other_number(5)


# Functions
# ===
# 
# Docstrings
# ---
# 
# Like many other definitions, functions can have docstrings.
# 
# * Docstrings are regular string values which you start the definition body with.
# * You can access an object's docstring using `help`.

# In[7]:


def factorial(n):
    """Compute factorial of n in the obious way."""
    if n == 0:
        return 1
    else:
        return factorial(n - 1) * n


# In[8]:


help(factorial)


# Functions
# ===
# 
# Functions are values
# ---
# 
# We can pass functions around just like other values, and call them.

# In[9]:


functions = [add_two, add_some_other_number]
for function in functions:
    print function(7)


# Simple anonymous functions can be created with `lambda`.

# In[10]:


functions.append(lambda x: x * 7)
for function in functions:
    print function(4)


# Functions
# ===
# 
# Higher-order functions
# ---
# 
# A function that takes a function as argument is a higher-order function.

# In[11]:


help(map)


# In[12]:


map(add_two, [1, 2, 3, 4])


# <div class="alert alert-success">
# <h1>Hands on!</h1>
# 
# <ol>
#   <li>Write a Python function that returns the maximum of two numbers.</li>
#   <li>Write a Python function that returns the maximum of three numbers. Try to reuse the first maximum of two numbers function.</li>
#   <li>Write a Python function that accepts a string as parameter. Next, it calculates and prints the number of upper case letters and lower case letters. Make us of the `isupper` and `islower` built in methods.</li>
# </ol>
# 
# </div>

# Comprehensions
# ===
# 
# List comprehensions
# ---
# 
# Similar to mathematical set notation (e.g., $\{ x ~|~ x \in \mathbf R \land x > 0\}$), we can create lists.

# In[13]:


[(x, x * x) for x in range(10) if x % 2]


# We can do the same thing using `map` and `filter`, but list comprehensions are often more readable.

# In[14]:


map(lambda x: (x, x * x), filter(lambda x: x %2, range(10)))


# Comprehensions
# ===
# 
# Set and dictionary comprehensions
# ---
# 
# Similar notation can be used for (non-empty) sets.

# In[15]:


{c for c in 'LUMC-standard' if 'a' <= c <= 'z'}


# And dictionaries.

# In[16]:


colors = ['red', 'white', 'blue', 'orange']
{c: len(c) for c in colors}


# Everything is an object
# ===
# 
# * Objects have properties and methods. 
# * Explore them using `dir(o)`, or by typing `o.<tab>` in the IPython interpreter.

# In[17]:


dir('abc')[-5:]


# In[18]:


help('abc'.upper)


# In[19]:


'abc'.upper()


# Code in files
# ===
# 
# Running code from a file
# ---

# In[20]:


cat examples/fsquare.py


# In[21]:


get_ipython().run_cell_magic('sh', '', 'python examples/fsquare.py\n')


# Code in files
# ===
# 
# Working with files in IPython
# ---
# 
# The `%run` magic runs the code from a file directly in IPython:

# In[22]:


get_ipython().run_line_magic('run', 'examples/fsquare.py')


# You can edit and run a file with `%edit`.

# In[23]:


get_ipython().run_line_magic('edit', 'examples/fsquare.py')


# Code in files
# ===
# 
# Saving your IPython session history to a file
# ---
# 
# Give the `%save` magic a name and a range of input lines and it will save them to a `.py` file with that name:
# 
#     In [4]: %save my_session 1-3
#     The following commands were written to file `my_session.py`:
#     a = 4
#     a += 3
#     b = a

# Further reading
# ===
# 
# * [The Python Tutorial](http://docs.python.org/2/tutorial/index.html)
#   <br>
#   From the official Python documentation.
# 
# 
# * [Learn Python The Hard Way](http://learnpythonthehardway.org/book/)
#   <br>
#   Book on learning Python by exercises, online available for free.
# 
# 
# * [The Hitchhiker's Guide to Python](http://docs.python-guide.org/en/latest/)
#   <br>
#   This opinionated guide exists to provide both novice and expert Python developers a best-practice handbook to the installation, configuration, and usage of Python on a daily basis.
# 
# 
# * [A Primer on Scientific Programming with Python](http://codingcat.com/knjige/python/A%20Primer%20on%20Scientific%20Programming%20with%20Python.pdf)
#   <br>
#   Complete PDF version of the book. The aim of this book is to teach computer programming using examples from mathematics and the natural sciences.
# 
# 
# * [Python Module of the Week](http://pymotw.com/)
#   <br>
#   Series of articles providing a tour of the Python standard library through short examples.

# Homework assignment
# ===
# 
# https://classroom.github.com/a/QU2iPYKn

# In[1]:


from IPython.display import HTML
def css_styling():
    styles = open('styles/custom.css', 'r').read()
    return HTML('<style>' + styles + '</style>')
css_styling()


# Acknowledgements
# ========
# 
# Martijn Vermaat
# 
# [Jeroen Laros](mailto:j.f.j.laros@lumc.nl)
# 
# Based on
# ---------
# [Python Scientific Lecture Notes](http://scipy-lectures.github.io/)
# 
# License
# --------
# [Creative Commons Attribution 3.0 License (CC-by)](http://creativecommons.org/licenses/by/3.0)