Question

我创建了一个循环来搜索CSV文件并返回带有指定关键字的行。标记else函数时，循环可以正常工作。

import csv
from tkinter import *
import tkinter.messagebox as box

master = Tk()

label1 = Label(master, text = 'User_ID', relief = 'groove', width = 40)
label2 = Label(master, text = 'User_Info', relief = 'groove', width = 40, height = 5)

e1 = Entry(master, relief = 'groove', width = 40)
e2 = Text(master, relief = 'groove', width = 40, height = 5, borderwidth = 2)

def enter():
    csvfile = open('stack_example.csv', 'r')
    read = csv.reader(csvfile)
    for row in read:
        if str(e1.get()) in row:
            e2.insert("1.0", row, 'r')
            #break
        #else:
            #box.showinfo('Search Result','Not Found')
            #master.mainloop()


button3 = Button(master, text = 'Retrieve File', relief = 'groove', width = 25, command=enter)

label1.grid( row = 1, column = 1, padx = 10 )
label2.grid( row = 2, column = 1, padx = 10 )

e1.grid( row = 1, column = 2, padx = 10 )
e2.grid( row = 2, column = 2, padx = 10 )

button3.grid( row = 3, column = 1, columnspan = 2)

但是，当else函数是代码的一部分时，循环将直接跳到else命令，而忽略if命令。上面产生的输出是将带有关键字的行从csv文件插入到文本小部件中。但是，下面的输出是一个显示框。（使用相同的entry关键字，即在csv文件中）

import csv
from tkinter import *
import tkinter.messagebox as box

master = Tk()

label1 = Label(master, text = 'User_ID', relief = 'groove', width = 40)
label2 = Label(master, text = 'User_Info', relief = 'groove', width = 40, height = 5)

e1 = Entry(master, relief = 'groove', width = 40)
e2 = Text(master, relief = 'groove', width = 40, height = 5, borderwidth = 2)

def enter():
    csvfile = open('stack_example.csv', 'r')
    read = csv.reader(csvfile)
    for row in read:
        if str(e1.get()) in row:
            e2.insert("1.0", row, 'r')
            #break
        else:
            box.showinfo('Search Result','Not Found')
            master.mainloop()


button3 = Button(master, text = 'Retrieve File', relief = 'groove', width = 25, command=enter)

label1.grid( row = 1, column = 1, padx = 10 )
label2.grid( row = 2, column = 1, padx = 10 )

e1.grid( row = 1, column = 2, padx = 10 )
e2.grid( row = 2, column = 2, padx = 10 )

button3.grid( row = 3, column = 1, columnspan = 2)

我的理解是，仅当if语句为false时，else命令才会执行。但是，else语句似乎用此代码覆盖了if语句。我不确定如何编写一个可以起作用的循环：

如果关键字在csvfile中
然后将带有关键字的行插入到空白小部件
如果关键字不在csvfile中
然后显示一个带有“未找到”文本的框

Answer 1

在<!DOCTYPE html> <html ng-app='myApp'> <head> <script data-require="angular.js@4.0.0" data-semver="4.0.0" src="https://ajax.googleapis.com/ajax/libs/angularjs/1.6.10/angular.min.js"></script> <script data-require="angular.js@4.0.0" data-semver="4.0.0" src="script.ts"></script> <script data-require="angular.js@4.0.0" data-semver="4.0.0" src="system.config.js"></script> <script data-require="angular.js@4.0.0" data-semver="4.0.0" src="tsconfig.json"></script> <link rel="stylesheet" href="style.css" /> <script src="script.js"></script> </head> <body ng-controller='myController'> <button ng-mousedown="mouseDown()" ng-mouseup="mouseUp()">Mouse Down</button> <br> <span>Doing something {{times}} times</span> </body> </html>循环中至少观察到一次any条件时，文本将更改。因此，您的template<typename T> void visit(T &&t) { std::cout << "Hi " << t << "!\n"; } void try_visit(std::any &&) { std::cout << "Unknown type\n"; } template<typename T, typename... Ts> void try_visit(std::any thing) { if(thing.type() == typeid(T)) { visit(std::any_cast<T>(thing)); return; } if constexpr(sizeof...(Ts) > 0) try_visit<Ts...>(std::move(thing)); else try_visit(std::move(thing)); } int main() { try_visit<short, int, double, bool, long>(std::any{42}); }语句代码可能仍在评估中，但是您还在同一循环中观察else的行为。试试这个：

for

如何使用循环使用python中的tkinter库解析csv文本

1 个答案: