[Python] Looping Techniques
When looping through dictionaries, the key and corresponding value can be retrieved at the same time using the iteritems() method.
When looping through a sequence, the position index and corresponding value can be retrieved at the same time using the enumerate() function.
To loop over two or more sequences at the same time, the entries can be paired with the zip() function.
To loop over a sequence in reverse, first specify the sequence in a forward direction and then call the reversed() function.
To loop over a sequence in sorted order, use the sorted() function which returns a new sorted list while leaving the source unaltered.
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[CODE]>>> knights = {'gallahad': 'the pure', 'robin': 'the brave'}
>>> for k, v in knights.iteritems():
... print k, v
...
gallahad the pure
robin the brave[/CODE]
When looping through a sequence, the position index and corresponding value can be retrieved at the same time using the enumerate() function.
[CODE]>>> for i, v in enumerate(['tic', 'tac', 'toe']):
... print i, v
...
0 tic
1 tac
2 toe[/CODE]
To loop over two or more sequences at the same time, the entries can be paired with the zip() function.
[CODE]>>> questions = ['name', 'quest', 'favorite color']
>>> answers = ['lancelot', 'the holy grail', 'blue']
>>> for q, a in zip(questions, answers):
... print 'What is your %s? It is %s.' % (q, a)
...
What is your name? It is lancelot.
What is your quest? It is the holy grail.
What is your favorite color? It is blue.[/CODE]
To loop over a sequence in reverse, first specify the sequence in a forward direction and then call the reversed() function.
[CODE]>>> for i in reversed(xrange(1,10,2)):
... print i
...
9
7
5
3
1[/CODE]
To loop over a sequence in sorted order, use the sorted() function which returns a new sorted list while leaving the source unaltered.
[CODE]>>> basket = ['apple', 'orange', 'apple', 'pear', 'orange', 'banana']
>>> for f in sorted(set(basket)):
... print f
...
apple
banana
orange
pear[/CODE]
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Subject: [Python] file로 읽은 것 한줄씩 루프처리하기
file handle로 받지 않고 sequence로 바로 저장해서 사용한다. [CODE]db = open("file.txt",'r').readlines() for line in db: print line[/CODE]
