Python Learning: 03

奎恩東特發表於2019-02-11
Python

　　　　An inch is worth a pound of gold, an inch of gold is hard to buy an inch of time.

  • Slice

　　　　When the scale of data is so large that we have to pick a short of the content, the best way is to use Slice.

    • Forward Slice
>>>L=range(1,101)
>>>L[1:]              #until the end
>>>L[:101]          #from the first
>>>L[1:100]
>>>L[1:101:2]     #pick one in two
    • Reverse Slice
>>>L=range(1,101)
>>>L[-1:]  
>>>L[:-1]
>>>L[-5:-1]
>>>L[-46::5]
  • Iteration

　　　　In Python, Iterations are done with “for … in …”. `For` loop in python can be used not only on Lists and Tuples, but alse on any other iterable objects. Therefore, the iterative operation is for a collection, whether the collection is ordered or unordered, we can always use the loop to extract each element of the collection in turn. The collection is a data structure containing a set of elements, and we have learnt List, Tuple, Set, Dict, Str, Unicode.

    • Index Iteration: Using enumerate() to get the Tuple of index and name and using zip() to conbine two lists into one
for index, name in enumerate(L):
    print index, `-`, name
>>> zip([10, 20, 30], [`A`, `B`, `C`])
[(10, `A`), (20, `B`), (30, `C`)]
    • The value of dict: values()  and  itervalues()
    • The key-value of dict: items()  and iteritems()

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