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In [1]:



    


import logging
import functools
import itertools

import numpy as np
logging.root.setLevel(logging.DEBUG)

Idiomatic





In [2]:



    


import this



    


















    






The Zen of Python, by Tim Peters

Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!

ugly





In [3]:



    


title = "title"
print("<html>")
print("<head>")
print("<title>" + title + "</title>")
print("</head>")
print("<body>")
print("<h1>" + title + "</h1>")
print("</body>")
print("</html>")



    


















    






<html>
<head>
<title>title</title>
</head>
<body>
<h1>title</h1>
</body>
</html>

















In [4]:



    


template = """<html>
 <head>
  <title>{title:s}</title>
 </head>
 <body>
 <h1>{title:s}</h1>
 </body>
</html>
"""
print(template.format(title=title))



    


















    






<html>
 <head>
  <title>title</title>
 </head>
 <body>
 <h1>title</h1>
 </body>
</html>


















In [5]:



    


a = [2,3,5]
sum_of_squares = 0
for i in range(len(a)):
    sum_of_squares = sum_of_squares + a[i] * a[i]
sum_of_squares



    


















    
Out[5]:








38

















In [6]:



    


sum(x**2 for x in a)



    


















    
Out[6]:








38

















In [11]:



    


(letter for letter in 'word')



    


















    
Out[11]:








<generator object <genexpr> at 0x7fcd84087a50>

















In [7]:



    


arr = np.array(a)
(arr**2).sum()



    


















    
Out[7]:








38

















In [13]:



    


colors = ["red", "yellow", "blue", "purple"]



    











In [14]:



    


for i in range(len(colors)):
    print(colors[i])



    


















    






red
yellow
blue
purple

















In [15]:



    


for color in colors:
    print(color)



    


















    






red
yellow
blue
purple

















In [18]:



    


sorted_colors = colors[:]
sorted_colors.sort()
for color in sorted_colors:
    print(color)



    


















    






blue
purple
red
yellow

















In [12]:



    


for color in sorted(colors):
    print(color)



    


















    






blue
purple
red
yellow

















In [13]:



    


for i in range(len(colors)):
    print("{}: {}".format(i, colors[i]))



    


















    






0: blue
1: purple
2: red
3: yellow

















In [14]:



    


for i, color in enumerate(colors):
    print("{}: {}".format(i, color))



    


















    






0: blue
1: purple
2: red
3: yellow

















In [15]:



    


variables = ["height", "length", "width", "volume"]
for i in range(len(variables)):
    variable = variables[i]
    color = colors[i]
    print("{i}: {color}, {variable}".format(i=i, color=color, variable=variable))



    


















    






0: blue, height
1: purple, length
2: red, width
3: yellow, volume

















In [19]:



    


zip([1,2,3], ['a', 'b', 'c'])



    


















    
Out[19]:








[(1, 'a'), (2, 'b'), (3, 'c')]

















In [16]:



    


variables = ["height", "length", "width", "volume"]
for i, (variable, color) in enumerate(zip(variables, colors)):
    print("{i}: {color}, {variable}".format(i=i, color=color, variable=variable))



    


















    






0: blue, height
1: purple, length
2: red, width
3: yellow, volume

















In [17]:



    


letters = ["C","a", "b"]
list(sorted(letters))



    


















    
Out[17]:








['C', 'a', 'b']

















In [18]:



    


def case_independent_cmp(a, b):
    return cmp(a.lower(), b.lower())
list(sorted(letters, cmp=case_independent_cmp))



    


















    
Out[18]:








['a', 'b', 'C']

















In [19]:



    


list(sorted(letters, key=str.lower))



    


















    
Out[19]:








['a', 'b', 'C']

Explicit is better than implicit





In [22]:



    


from math import *
from numpy import *
import logging

log([1,2,3, 2])



    


















    
Out[22]:








array([ 0.        ,  0.69314718,  1.09861229,  0.69314718])

















In [23]:



    


from numpy import *
from math import *
try:
    log([1,2,3, 2])
except:
    logging.exception("that does not compute")



    


















    






ERROR:root:that does not compute
Traceback (most recent call last):
  File "<ipython-input-23-f2e5e3862da6>", line 4, in <module>
    log([1,2,3, 2])
TypeError: a float is required

















In [22]:



    


import numpy as np
np.log([1,2,3, 2])



    


















    
Out[22]:








array([ 0.        ,  0.69314718,  1.09861229,  0.69314718])

















In [24]:



    


"it's %d o'clock" % (3,)



    


















    
Out[24]:








"it's 3 o'clock"

















In [23]:



    


try:
    "It is " +3 + " o'clock"
except:
    logging.exception("Strong typing please!")



    


















    






ERROR:root:Strong typing please!
Traceback (most recent call last):
  File "<ipython-input-23-64cdd9f2df20>", line 2, in <module>
    "It is " + 3 + " o'clock"
TypeError: cannot concatenate 'str' and 'int' objects

















In [24]:



    


"It is {hours:d} o'clock".format(hours=3)



    


















    
Out[24]:








"It is 3 o'clock"

Simple/Complex/Complicated





In [25]:



    


DEBUG = True
def calculate():
    if DEBUG:
        print("starting calculate")
    1 + 1
    if DEBUG:
        print("finished calculate")
calculate()



    


















    






starting calculate
finished calculate

















In [26]:



    


def log_call(func):
    logging.debug("starting {}")
    func()
    logging.debug("finished {}")
    
@log_call
def calculate():
    1 + 1



    


















    






DEBUG:root:starting {}
DEBUG:root:finished {}

Flat is better than nested





In [27]:



    


# in java:
# import org.apache.xerces.impl.xpath.regex.EXIRegularExpression;
import re



    











In [28]:



    


import requests
import xml.etree.ElementTree

url = 'http://live.waterbase.nl/metis/cgi-bin/mivd.pl?action=value&code=DOOVBWT&format=xml&lang=nl&order=code&type=loc'
doc = xml.etree.ElementTree.fromstring(requests.get(url).content)
doc.getchildren()[0].\
    getchildren()[0].\
    getchildren()[0].\
    getchildren()[2].\
    getchildren()[0].\
    getchildren()[0].\
    getchildren()[0].\
    getchildren()[0].\
    text



    


















    






INFO:requests.packages.urllib3.connectionpool:Starting new HTTP connection (1): live.waterbase.nl
DEBUG:requests.packages.urllib3.connectionpool:"GET /metis/cgi-bin/mivd.pl?action=value&code=DOOVBWT&format=xml&lang=nl&order=code&type=loc HTTP/1.1" 200 None










    
Out[28]:








'131200,562950'

















In [29]:



    


doc.find('.//gml:Coordinates', namespaces={'gml': 'http://www.opengis.net/gml'}).text



    


















    
Out[29]:








'131200,562950'

Errors should never pass silent





In [30]:



    


try:
    pay_salary(amount)
except:
    pass

Unless explicitly silenced





In [25]:



    


def transfer(amount, account):
    if not isinstance(amount, int):
        raise TypeError("expected integer, got %s" % (type(amount), ))
    print("paying %d to %s" % (amount, account))
    
extra = 0
amount = 23.43
for i in range(5):
    try:
        # try if we can transfer
        transfer(amount, "bank")
    except TypeError:
        # amount is a floating point
        transfer(int(amount), "bank")
        extra += amount - int(amount)
        if extra > 1:
            transfer(int(extra), "fedor")
            extra -= int(extra)



    


















    






paying 23 to bank
paying 23 to bank
paying 23 to bank
paying 1 to fedor
paying 23 to bank
paying 23 to bank
paying 1 to fedor

















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