idiomatic.py

''' from Transforming Code into Beautiful, Idiomatic Python
by Raymond Hettinger'''

for i in [0, 1, 2, 3, 4, 5]:
    print i**2

for i in range(6):
    print i**2

for i in xrange(6):
    print i**2

colors = ['red', 'green', 'blue', 'yellow']

# don't do this
for i in range (len(colors)):
    print colors[i]

# do this
for color in colors:
    print color

# don't
for i in range(len(colors) -1, -1, -1):
    print colors[i]

# do
for color in reversed(colors):
    print color

# don't
for i in range(len(colors)):
    print i, '-->' colors[i]

# do
for i, color in enumerate(colors):
    print i, '-->', colors[i]

''' Looping over two collections '''
names = ['raymond', 'rachel', 'matthew']
colors = ['red', 'green', 'blue', 'yellow']

# don't
n = min(len(names), len(colors))
for i in range(n):
    print names[i], '-->', colors[i]

# don't
for name, color in zip(names, colors):
    print name, '-->', color

# do
for name, color in izip(names, colors):
    print name, '-->', color

''' Looping in sorted order '''
colors = ['red', 'green', 'blue', 'yellow']

for color in sorted(colors):
    print color

for color in sorted(colors, reverse=True):
    print color

def compare_length(c1, c2):
    if len(c1) < len(c2): return -1
    if len(c1) > len(c2): return 1
    return 0

# don't
print sorted(colors, cmp=compare_length)

# do
print sorted(colors, key=len)

# Call a function until a sentinel value

blocks = []
while True:
    block = f.read(32)
    if block == '':
        break
    blocks.append(block)

blocks = []
for block in iter(partial(f.read, 32), ''):
    blocks.append(block)

# Distinguishing mulitiple exit points in loops
def find(seq, target):
    found = False
    for i, value in enumerate(seq):
        if value == tgt:
            found = True
            break
    if not found:
        return -1
    return i

def find(seq, target):
    for i, value in enumerate(seq):
        if value == tgt:
            break
    else:
        return -1
    return i

'''Dictionary Skills
* Mastering dictionaries is a fundamental Python Skill
* They are the fundamental tool for expressing relationships,
    linking, counting, and grouping.    '''

# Looping over the dictionary keys
d = ('matthew': 'blue', 'rachel': 'green', 'raymond': 'red')

for k in d:
    print k

for k in d.keys():
    if k.startswith('r'):
        del d[k]

# Looping over a dictionary keys and values

for k in d:
    print k, '-->', d[k]

for k, v in d.items():
    print k, '-->', v
#====================================
# Construct a dictionary from pairs

names = ['raymond', 'rachel', 'matthew']
colors = ['red', 'green', 'blue']

d = dict(izip(names, colors))
('matthew': 'blue', 'rachel': 'green', 'raymond': 'red')

# Counting with dictionaries

colors = ['red', 'green', 'red', 'blue', 'green', 'red']

d = {}
for color in colors:
    if color not in d:
        d[color] = 0
    d[color] += 1

{'blue':1, 'green':2, 'red':3}

# simplified
d = {}
for color in colors:
    d[color] = d.get(color, 0) + 1

d = defaultdict(int)
for color in colors:
    d[color] += 1


### Grouping with dictionaries -- Part I
names = ['raymond', 'rachel', 'matthew', 'roger',
         'betty', 'melissa', 'judith', 'charlie']

d = {}
for name in names:
    key = len(name)
    if key not in d:
        d[key] = []
    d[key].append(name)

# Grouping with dictionaries == Part II

d = {}
for name in names:
    key = len(name)
    d.setdefault(key, []).append(name)

d = defaultdict(list)
for name in names:
    key = len(name)
    d[key].append(name)

"""==================
28:00 minutes """
# popitem
# linking dictionaries
# ChainMap
# Improving Clarity
# positional arguments and indicies
twitter_search('@obama', retweets=False, numtweets=20, popular=True)