In [1]:

    

from __future__ import absolute_import, division, print_function


    

In [2]:

    

# Create a [list] 
days = ['Monday', # multiple lines 
        'Tuesday', # acceptable 
        'Wednesday',
        'Thursday',
        'Friday',
        'Saturday',
        'Sunday', 
       ] # trailing comma is fine!


    

In [3]:

    

days


    

    
Out[3]:





['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']

In [4]:

    

# Simple for-loop
for day in days:
    print(day)


    

    




Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday

In [5]:

    

# Double for-loop
for day in days:
    for letter in day:
        print(letter)


    

    




M
o
n
d
a
y
T
u
e
s
d
a
y
W
e
d
n
e
s
d
a
y
T
h
u
r
s
d
a
y
F
r
i
d
a
y
S
a
t
u
r
d
a
y
S
u
n
d
a
y

In [6]:

    

print(days)


    

    




['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']

In [7]:

    

print(*days)


    

    




Monday Tuesday Wednesday Thursday Friday Saturday Sunday

In [10]:

    

# Double for-loop
for day in days:
    for letter in day:
        print(letter)
    print()


    

    




M
o
n
d
a
y

T
u
e
s
d
a
y

W
e
d
n
e
s
d
a
y

T
h
u
r
s
d
a
y

F
r
i
d
a
y

S
a
t
u
r
d
a
y

S
u
n
d
a
y

In [12]:

    

for day in days:
    for letter in day:
        print(letter.lower())


    

    




m
o
n
d
a
y
t
u
e
s
d
a
y
w
e
d
n
e
s
d
a
y
t
h
u
r
s
d
a
y
f
r
i
d
a
y
s
a
t
u
r
d
a
y
s
u
n
d
a
y

In [13]:

    

length_of_days = [len(day) for day in days]
length_of_days


    

    
Out[13]:





[6, 7, 9, 8, 6, 8, 6]

In [14]:

    

letters = [letter for day in days
                    for letter in day]


    

In [15]:

    

print(letters)


    

    




['M', 'o', 'n', 'd', 'a', 'y', 'T', 'u', 'e', 's', 'd', 'a', 'y', 'W', 'e', 'd', 'n', 'e', 's', 'd', 'a', 'y', 'T', 'h', 'u', 'r', 's', 'd', 'a', 'y', 'F', 'r', 'i', 'd', 'a', 'y', 'S', 'a', 't', 'u', 'r', 'd', 'a', 'y', 'S', 'u', 'n', 'd', 'a', 'y']

In [17]:

    

letters = [letter for day in days for letter in day]
print(letters)


    

    




['M', 'o', 'n', 'd', 'a', 'y', 'T', 'u', 'e', 's', 'd', 'a', 'y', 'W', 'e', 'd', 'n', 'e', 's', 'd', 'a', 'y', 'T', 'h', 'u', 'r', 's', 'd', 'a', 'y', 'F', 'r', 'i', 'd', 'a', 'y', 'S', 'a', 't', 'u', 'r', 'd', 'a', 'y', 'S', 'u', 'n', 'd', 'a', 'y']

In [18]:

    

[num for num in xrange(10) if num % 2]


    

    
Out[18]:





[1, 3, 5, 7, 9]

In [19]:

    

[num for num in xrange(10) if num % 2 else "doesn't work"]


    

    




  File "<ipython-input-19-2891a8980b2c>", line 1
    [num for num in xrange(10) if num % 2 else "doesn't work"]
                                             ^
SyntaxError: invalid syntax

In [20]:

    

[num if num % 2 else "works" for num in xrange(10)]


    

    
Out[20]:





['works', 1, 'works', 3, 'works', 5, 'works', 7, 'works', 9]

In [22]:

    

[num for num in xrange(10)]


    

    
Out[22]:





[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

In [23]:

    

sorted_letters = sorted([x.lower() for x in letters])
print(sorted_letters)


    

    




['a', 'a', 'a', 'a', 'a', 'a', 'a', 'a', 'd', 'd', 'd', 'd', 'd', 'd', 'd', 'd', 'e', 'e', 'e', 'f', 'h', 'i', 'm', 'n', 'n', 'n', 'o', 'r', 'r', 'r', 's', 's', 's', 's', 's', 't', 't', 't', 'u', 'u', 'u', 'u', 'w', 'y', 'y', 'y', 'y', 'y', 'y', 'y']

In [24]:

    

unique_sorted_letters = sorted(set(sorted_letters))


    

In [25]:

    

print("There are", len(unique_sorted_letters), "unique letters in the days of the week.")
print("They are:", ''.join(unique_sorted_letters))


    

    




There are 15 unique letters in the days of the week.
They are: adefhimnorstuwy

In [28]:

    

print("They are:", '; '.join(unique_sorted_letters))


    

    




They are: a; d; e; f; h; i; m; n; o; r; s; t; u; w; y

In [ ]:

    

def first_three(input_string):
    """Takes an input string and returns the first 3 characters."""
    return input_string[:3]


    

In [ ]:

    

import numpy as np


    

In [ ]:

    

# tab
np.linspace()


    

In [ ]:

    

[first_three(day) for day in days]


    

In [ ]:

    

def last_N(input_string, number=2):
    """Takes an input string and returns the last N characters."""
    return input_string[-number:]


    

In [ ]:

    

[last_N(day, 4) for day in days if len(day) > 6]


    

In [ ]:

    

from math import pi

print([str(round(pi, i)) for i in xrange(2, 9)])


    

In [ ]:

    

list_of_lists = [[i, round(pi, i)] for i in xrange(2, 9)]
print(list_of_lists)


    

In [ ]:

    

for sublist in list_of_lists:
    print(sublist)


    

In [ ]:

    

# Let this be a warning to you!

# If you see python code like the following in your work:

for x in range(len(list_of_lists)):
    print("Decimals:", list_of_lists[x][0], "expression:", list_of_lists[x][1])


    

In [ ]:

    

print(list_of_lists)

# Change it to look more like this: 

for decimal, rounded_pi in list_of_lists:
    print("Decimals:", decimal, "expression:", rounded_pi)


    

In [ ]:

    

# enumerate if you really need the index

for index, day in enumerate(days):
    print(index, day)


    

In [4]:

    

from IPython.display import IFrame, HTML
HTML('<iframe src=https://en.wikipedia.org/wiki/Hash_table width=100% height=550></iframe>')


    

    
Out[4]:

In [30]:

    

fellows = ["Jonathan", "Alice", "Bob"]
universities = ["UCSD", "UCSD", "Vanderbilt"]


    

In [31]:

    

for x, y in zip(fellows, universities):
    print(x, y)


    

    




Jonathan UCSD
Alice UCSD
Bob Vanderbilt

In [32]:

    

# Don't do this
{x: y for x, y in zip(fellows, universities)}


    

    
Out[32]:





{'Alice': 'UCSD', 'Bob': 'Vanderbilt', 'Jonathan': 'UCSD'}

In [34]:

    

# Doesn't work like you might expect
{zip(fellows, universities)}


    

    




---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-34-b238f9ef0459> in <module>()
      1 # Doesn't work like you might expect
----> 2 {zip(fellows, universities)}

TypeError: unhashable type: 'list'

In [33]:

    

dict(zip(fellows, universities))


    

    
Out[33]:





{'Alice': 'UCSD', 'Bob': 'Vanderbilt', 'Jonathan': 'UCSD'}

In [35]:

    

fellows


    

    
Out[35]:





['Jonathan', 'Alice', 'Bob']

In [36]:

    

fellow_dict = {fellow.lower(): university 
                   for fellow, university in zip(fellows, universities)}


    

In [37]:

    

fellow_dict


    

    
Out[37]:





{'alice': 'UCSD', 'bob': 'Vanderbilt', 'jonathan': 'UCSD'}

In [38]:

    

fellow_dict['bob']


    

    
Out[38]:





'Vanderbilt'

In [ ]:

    

rounded_pi = {i:round(pi, i) for i in xrange(2, 9)}


    

In [ ]:

    

rounded_pi[5]


    

In [ ]:

    

sum([i ** 2 for i in range(10)])


    

In [ ]:

    

sum(i ** 2 for i in range(10))


    

In [ ]:

    

huh = (i ** 2 for i in range(10))


    

In [ ]:

    

huh.next()