Python for the Java Programmer - Part 3
Three more Python tricks (ok, one is about a standard python module) that I always get wrong the first time.
Reading a Web Page
import urllib2 page = urllib2.urlopen('http://www.infobart.com') content = page.read() # content is now a "byte string" (ascii-like) # which does not support unicode. # Do this to properly encode your content: encoding=page.headers['content-type'].split('charset=')[-1] ucontent = unicode(content, encoding) # Reference: http://stackoverflow.com/questions/1020892/urllib2-read-to-unicode [/cc]
Sorting Lists
>>> l1 = ['BBB','aaa','ccc','DDD'] >>> # Standard sort >>> sorted(l1) ['BBB', 'DDD', 'aaa', 'ccc'] >>> >>> # Passing a function that will be applied >>> # to each value before sorting. Good for >>> # standalone function >>> sorted(l1, key=str.lower) ['aaa', 'BBB', 'ccc', 'DDD'] >>> >>> # Using a lambda that will return the key >>> # for each value: better if you want to invoke >>> # an instance method. >>> sorted(l1, key=lambda s: s.lower()) ['aaa', 'BBB', 'ccc', 'DDD'] >>> >>> # Also works with list.sort() >>> l1.sort(key=lambda s:s.lower()) >>> l1 ['aaa', 'BBB', 'ccc', 'DDD']
String Formatting
b1 = True f1 = 7.0/22.0 i1 = 234 s1 = 'World!' s = 'Hello ' + s1 + str(b1) + str(f1) + str(i1) # s = 'Hello World!True0.318181818182234' s = 'Hello %s %r %.2f %i' % (s1, b1, f1, i1) # s = 'Hello World! True 0.32 234' # Preferred way of formatting a string s = 'Hello {0} {1} {2:.2} {3}'.format(s1, b1, f1, i1) # s = 'Hello World! True 0.32 234'
