从列表中

时间：2017-11-01 21:16:35

标签： python python-2.7

我从列表中获取元素时遇到问题。当我按下键盘的Page down按钮时，它将调用PageDown函数，因为它将跳过7个元素，它将从列表中获取7个下一个元素：

['108 Sky Atlantic', '401 Sky Sports 1 UK', '402 SKY Sports 2 UK', '403 Sky Sports 3 UK', '404 Sky Sports 4 UK', '405 Sky Sports 5 UK', '406 Sky Sports News HQ']

当我点击键盘的向下箭头按钮时，它将跳过7个元素，但它不会获取406 Sky Sports News HQ之后的7个元素，因为它将获取它将在413 Eurosport 1 UK之后出现的元素{1}}所以channels_list会显示不正确的内容：

['414 Eurosport 2 UK', '415 BT Sport 1', '416 BT Sport 2',
 '417 At the Races', '418 BT Sport ESPN', '419 MUTV', '420 Chelsea TV']

应该是：

['407 Sky Sports F1', '408 Sky Sports 1 HD', '409 Sky Sports 2 HD', '410 Sky Sports 3 HD', '411 Sky Sports 4 HD', '412 Sky Sports 5 HD', '413 Eurosport 1 UK']

以下是代码：

def PageDown(self):
    self.channel = [
        '101 BBC One S East', '102 BBC Two', '103 ITV', '104 Channel 4', 
        '105 Channel 5', '106 Sky One', '107 Sky Living', '108 Sky Atlantic', 
        '401 Sky Sports 1 UK', '402 SKY Sports 2 UK', '403 Sky Sports 3 UK', 
        '404 Sky Sports 4 UK', '405 Sky Sports 5 UK', '406 Sky Sports News HQ', 
        '407 Sky Sports F1', '408 Sky Sports 1 HD', '409 Sky Sports 2 HD', 
        '410 Sky Sports 3 HD', '411 Sky Sports 4 HD', '412 Sky Sports 5 HD', 
        '413 Eurosport 1 UK', '414 Eurosport 2 UK', '415 BT Sport 1', 
        '416 BT Sport 2', '417 At the Races', '418 BT Sport ESPN', '419 MUTV', 
        '420 Chelsea TV', '421 Eir Sport 1', '422 Eir Sport 2']

    channels_list = list()
    channels_Index += 7

    for i, start_ch in enumerate(self.channel):
        if start_ch == channel:
            channels_list = 
                self.channel[i+self.channels_Index:i+self.channels_Index+7]

我期望实现的是当我点击键盘的向下翻页按钮时，我想跳过7个元素并每次获取7个元素。

这是例如：

当我点击页面向下按钮时，我想跳过7个元素并获取显示如下所示的7个下一个元素：     ['108 Sky Atlantic'，'401 Sky Sports 1 UK'，'402 SKY Sports 2 UK'，'403 Sky Sports 3 UK'，'404 Sky Sports 4 UK'，'405 Sky Sports 5 UK'，'406 Sky体育新闻总部']

所以当我点击页面向下按钮时，我想获得7个下一个元素：

['407 Sky Sports F1', '408 Sky Sports 1 HD', '409 Sky Sports 2 HD', '410 Sky Sports 3 HD', '411 Sky Sports 4 HD', '412 Sky Sports 5 HD', '413 Eurosport 1 UK']

当我再次点击页面向下按钮时，我想获取7个下一个元素：

['414 Eurosport 2 UK', '415 BT Sport 1', '416 BT Sport 2', '417 At the Races', '418 BT Sport ESPN', '419 MUTV', '420 Chelsea TV']

当我最后再次点击页面向下按钮时，我想获取接近列表末尾的7个元素，使其显示如下：

['416 BT Sport 2', '417 At the Races', '418 BT Sport ESPN', '419 MUTV', '420 Chelsea TV', '421 Eir Sport 1', '422 Eir Sport 2']

你能否告诉我一个例子，当我点击键盘的页面向下按钮时，我每次跳过7个元素并从列表中取出7个元素？

3 个答案:

答案 0 :(得分：1)

移动线

channels_Index += 7

现在应该可以了。将它放在循环之后，以便可以再次调用它。

答案 1 :(得分：1)

这演示了一次滚动浏览7个频道，关键部分是next_seven_channels = self.all_channels[self.channel_index:end_index] 

try:
    import Tkinter as tk
except:
    import tkinter as tk

class app(tk.Tk):
    def __init__(self):
        tk.Tk.__init__(self)
        self.all_channels =  [
        '101 BBC One S East', '102 BBC Two', '103 ITV', '104 Channel 4', 
        '105 Channel 5', '106 Sky One', '107 Sky Living', '108 Sky Atlantic', 
        '401 Sky Sports 1 UK', '402 SKY Sports 2 UK', '403 Sky Sports 3 UK', 
        '404 Sky Sports 4 UK', '405 Sky Sports 5 UK', '406 Sky Sports News HQ', 
        '407 Sky Sports F1', '408 Sky Sports 1 HD', '409 Sky Sports 2 HD', 
        '410 Sky Sports 3 HD', '411 Sky Sports 4 HD', '412 Sky Sports 5 HD', 
        '413 Eurosport 1 UK', '414 Eurosport 2 UK', '415 BT Sport 1', 
        '416 BT Sport 2', '417 At the Races', '418 BT Sport ESPN', '419 MUTV', 
        '420 Chelsea TV', '421 Eir Sport 1', '422 Eir Sport 2']
        self.channel_index = 0

        self.print_channels = tk.Button(self,text="Page Down",
                                        font=("Calibri",30,"bold"),
                                        foreground="DodgerBlue2",
                                        command=self.PageDown)
        self.print_channels.pack()

    def PageDown(self,event=None):
        end_index = self.channel_index + 7
        if end_index > len(self.all_channels):
            end_index -= len(self.all_channels) - end_index   
        next_seven_channels = self.all_channels[self.channel_index:end_index]
        self.channel_index += 7
        if self.channel_index > len(self.all_channels):
            self.channel_index = 0
        print (next_seven_channels)

root = app()
root.mainloop()

如果我理解正确，要立即显示前7个频道，请在节目开始后拨打self.PageDown()，如下所示：

try:
    import Tkinter as tk
except:
    import tkinter as tk

class app(tk.Tk):
    def __init__(self):
        tk.Tk.__init__(self)
        self.all_channels =  [
        '101 BBC One S East', '102 BBC Two', '103 ITV', '104 Channel 4', 
        '105 Channel 5', '106 Sky One', '107 Sky Living', '108 Sky Atlantic', 
        '401 Sky Sports 1 UK', '402 SKY Sports 2 UK', '403 Sky Sports 3 UK', 
        '404 Sky Sports 4 UK', '405 Sky Sports 5 UK', '406 Sky Sports News HQ', 
        '407 Sky Sports F1', '408 Sky Sports 1 HD', '409 Sky Sports 2 HD', 
        '410 Sky Sports 3 HD', '411 Sky Sports 4 HD', '412 Sky Sports 5 HD', 
        '413 Eurosport 1 UK', '414 Eurosport 2 UK', '415 BT Sport 1', 
        '416 BT Sport 2', '417 At the Races', '418 BT Sport ESPN', '419 MUTV', 
        '420 Chelsea TV', '421 Eir Sport 1', '422 Eir Sport 2']
        self.channel_index = 0

        self.print_channels = tk.Button(self,text="Page Down",
                                        font=("Calibri",30,"bold"),
                                        foreground="DodgerBlue2",
                                        command=self.PageDown)
        self.print_channels.pack()
        self.PageDown() # added code <----

    def PageDown(self,event=None):
        end_index = self.channel_index + 7
        if end_index > len(self.all_channels):
            end_index -= len(self.all_channels) - end_index   
        next_seven_channels = self.all_channels[self.channel_index:end_index]
        self.channel_index += 7
        if self.channel_index > len(self.all_channels):
            self.channel_index = 0
        print (next_seven_channels)

root = app()
root.mainloop()

或者在程序启动时跳过显示前7个频道：

try:
    import Tkinter as tk
except:
    import tkinter as tk

class app(tk.Tk):
    def __init__(self):
        tk.Tk.__init__(self)
        self.all_channels =  [
        '101 BBC One S East', '102 BBC Two', '103 ITV', '104 Channel 4', 
        '105 Channel 5', '106 Sky One', '107 Sky Living', '108 Sky Atlantic', 
        '401 Sky Sports 1 UK', '402 SKY Sports 2 UK', '403 Sky Sports 3 UK', 
        '404 Sky Sports 4 UK', '405 Sky Sports 5 UK', '406 Sky Sports News HQ', 
        '407 Sky Sports F1', '408 Sky Sports 1 HD', '409 Sky Sports 2 HD', 
        '410 Sky Sports 3 HD', '411 Sky Sports 4 HD', '412 Sky Sports 5 HD', 
        '413 Eurosport 1 UK', '414 Eurosport 2 UK', '415 BT Sport 1', 
        '416 BT Sport 2', '417 At the Races', '418 BT Sport ESPN', '419 MUTV', 
        '420 Chelsea TV', '421 Eir Sport 1', '422 Eir Sport 2']
        self.channel_index = 7 # changed code <----

        self.print_channels = tk.Button(self,text="Page Down",
                                        font=("Calibri",30,"bold"),
                                        foreground="DodgerBlue2",
                                        command=self.PageDown)
        self.print_channels.pack()

    def PageDown(self,event=None):
        end_index = self.channel_index + 7
        if end_index > len(self.all_channels):
            end_index -= len(self.all_channels) - end_index   
        next_seven_channels = self.all_channels[self.channel_index:end_index]
        self.channel_index += 7
        if self.channel_index > len(self.all_channels):
            self.channel_index = 0
        print (next_seven_channels)

root = app()
root.mainloop()

答案 2 :(得分：1)

您更改了channels_Index的值，这是一个您尚未在代码中发布的全局变量（我假设;否则python将抛出NameError），但您读取的值{{1 }}。你可能意味着self.channels_Index

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