[Python] commonly used combination data types __python

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Original link: http://blog.csdn.net/humanking7/article/details/45276769 python common combination data type 1. Sequence type 1.1. List: Use [] to create, can be changed (change the content after the ID unchanged), support the modification, different from the string and integral type. such as:

    >>list1 = [' This ', ' is ', ' a ', ' pig ', '. ']
    >>list1[0]
    >> ' This '
    >>list1[0][0]
    >> ' T '

1.2. Tuples: Use () to create, can not be changed, in addition to the list is no different. such as:

    >>t1 = ("This", "is", "a", "Pig", ".")
    >>t1[0]
    >> ' This '
    >>t1[0][0]
    >> ' T '

1.3. String: Also belongs to the sequence type, and can be sliced operation.

    >>name = ' Jerry '
    >>name[0]
    ' j '
    >>name[0:1]  #后面位置不显示
    ' j '
    >>name[ 0:2]
    ' JE '
    >>name[:2]  #从0开始, if you do not write
    ' je '
    >>name[2:]  #到结尾, if you do not write
    ' Rry '
    >>name[0:4]
    ' Jerr '
    >>name[0:4:2]   #第3个数字表示了步进长度为2
    ' JR '

Note: The slice itself creates a new memory object, because the string itself is not variable, so the slice itself is the new object. The original film itself has not changed anything. 2. Collection type:

set: A piece of data is put together in a haphazard, no concept of order, and it also removes duplicate data . 3. Mapping Type:

Dictionary: A bit like a key-value pair, K-v set

    >>dic1 = {' x ': #, ' y ': 27.49, ' z ':
    >>dic1[' x ']
    >>dic2 = {1:32, 2:27.49, 3:65}
    >>dic2[2]
    27.49
    >>print "% (x) -10d% (y) 0.3g"%dic1   #print用法见后面         27.5

Note that the dictionary is a mutable object and a tuple is an immutable sequence. The combination data type is also an object, so it can be nested, such as: [' Hello ', ' world ', [1,2,3]] in essence, lists and tuples do not actually store data, but rather hold object reference tuples, lists, and string data types that are "size", i.e., Its length can be used in a built-in function len () to measure the Append () method in a specific "method" list that a Python object can have its invocation can be used to supplement the new element