Python | 用列表的前一半和后一半元素创建两个列表

不念不忘少年蓝@ 2023-03-05 04:29 18阅读 0赞

**Given a list, and we have to create two lists from first half elements and second half elements of a list in Python.**

**给定一个列表，我们必须在Python中从列表的前一半元素和后一半元素创建两个列表。**

**Example:**

**例：**

Input:
        list:  [10, 20, 30, 40, 50, 60]
    
        Output:
        list1: [10, 20, 30]
        list2: [40, 50, 60]

**Logic:**

**逻辑：**

*  First take list (Here, we are taking list with 6 elements).
    
    第一个清单(此处，我们列出了包含6个元素的清单)。
 *  To get the elements from/till specified index, use list\[n1:n2\] notation.
    
    要从/直到指定索引获取元素，请使用list \[n1：n2\]表示法。
 *  To get first half elements, we are using list\[:3\], it will return first 3 elements of the list.
    
    为了获得前半个元素，我们使用list \[：3\] ，它将返回列表的前三个元素。
 *  And, to get second half elements, we are using list\[3:\], it will return elements after first 3 elements. In this example, we have only 6 elements, so next 3 elements will be returned.
    
    并且，要获取后半个元素，我们使用list \[3：\] ，它将在前三个元素之后返回元素。 在此示例中，我们只有6个元素，因此将返回下3个元素。
 *  Finally, print the lists.
    
    最后，打印列表。

**Program:**

**程序：**

# define a list 
    list = [10, 20, 30, 40, 50, 60]
    
    # Create list1 with half elements (first 3 elements)
    list1 = list [:3]
    # Create list2 with next half elements (next 3 elements)
    list2 = list [3:]
    
    # print list (s)
    print "list : ",list
    print "list1: ",list1
    print "list2: ",list2

**Output**

**输出量**

list :  [10, 20, 30, 40, 50, 60]
        list1:  [10, 20, 30]
        list2:  [40, 50, 60]

### 使用列表\[：3\]和列表\[3：\]的列表\[0：3\]和列表\[3：6\] **(**Using list\[0:3\] and list\[3:6\] instaed of list\[:3\] and list\[3:\]**)** ###

We can also use list\[0:3\] instead of list\[:3\] to get first 3 elements and list\[3:6\] instead of list\[3:\] to get next 3 elements after first 3 elements.

我们还可以使用list \[0：3\]代替list \[：3\]获得前3个元素，并使用list \[3：6\]代替list \[3：\]获得前3个元素之后的下3个元素。

**Consider the program:**

**考虑该程序：**

# define a list 
    list = [10, 20, 30, 40, 50, 60]
    
    # Create list1 with half elements (first 3 elements)
    list1 = list [0:3]
    # Create list2 with next half elements (next 3 elements)
    list2 = list [3:6]
    
    # print list (s)
    print "list : ",list
    print "list1: ",list1
    print "list2: ",list2

**Output**

**输出量**

list :  [10, 20, 30, 40, 50, 60]
        list1:  [10, 20, 30]
        list2:  [40, 50, 60]

### 通过考虑清单的长度 **(**By considering length of the list**)** ###

Let suppose list has n elements, then we can use list\[0:n/2\] and list\[n/2:n\].

假设list有n个元素，那么我们可以使用list \[0：n / 2\]和list \[n / 2：n\] 。

**Consider the program:**

**考虑该程序：**

**If there are ODD numbers of elements in the list, program will display message "List has ODD number of elements." And exit.**

**如果列表中包含奇数个元素，程序将显示消息“列表中包含奇数个元素”。** **然后退出。**

# define a list 
    list = [10, 20, 30, 40, 50, 60]
    
    # get the length of the list 
    n = len(list)
    
    # condition to check length is EVEN or not
    # if lenght is ODD, show message and exit
    if( n%2 != 0 ):
        print "List has ODD number of elements."
        exit()
        
    # Create list1 with half elements (first 3 elements)
    list1 = list [0:n/2]
    # Create list2 with next half elements (next 3 elements)
    list2 = list [n/2:n]
    
    # print list (s)
    print "list : ",list
    print "list1: ",list1
    print "list2: ",list2

**Output**

**输出量**

list :  [10, 20, 30, 40, 50, 60]
        list1:  [10, 20, 30]
        list2:  [40, 50, 60]

> 翻译自: [https://www.includehelp.com/python/create-two-lists-with-first-half-and-second-half-elements-of-a-list.aspx][https_www.includehelp.com_python_create-two-lists-with-first-half-and-second-half-elements-of-a-list.aspx]

[https_www.includehelp.com_python_create-two-lists-with-first-half-and-second-half-elements-of-a-list.aspx]: https://www.includehelp.com/python/create-two-lists-with-first-half-and-second-half-elements-of-a-list.aspx