# coding: utf-8

# Functions help extract out common code blocks.
# 
# Let's define a function `print_greeting()`.

# In[1]:

def print_greeting():
    print("Hi there, how are you?")
    print("Long time no see.")


# And call it:

# In[2]:

print_greeting()


# That's a bit impersonal.

# In[3]:

def print_greeting(name):
    print("Hi there, {0}, how are you?".format(name))
    print("Long time no see.")


# In[4]:

print_greeting("Andreas")


# But we might not know their name.
# 
# (And we just changed the interface of `print_greeting`!)

# In[6]:

def print_greeting(name="my friend"):
    print("Hi there, {0}, how are you?".format(name))
    print("Long time no see.")


# In[7]:

print_greeting("Andreas")
print_greeting()


# ----

# Function parameters work like variables.
# 
# So what does this do?

# In[8]:

def my_func(my_list):
    my_list.append(5)
    
l = [1,2,3]
my_func(l)
print(l)


# Can be very surprising!
# 
# Define a better function `my_func_2`:

# In[9]:

def my_func_2(my_list):
    return my_list + [5]


# In[10]:

l = [1,2,3]
l2 = my_func_2(l)
print(l)
print(l2)