无法访问已声明的全局变量

Question

我尝试声明一个存储返回的数据库对象的全局变量。但它引发了 NameError 异常。 尝试将返回的对象声明为全局对象，但没有任何有用的事情发生。

import tkinter as tk
import mysql.connector
import tkinter.messagebox
# import connect
root = tk.Tk()
root.title("Login To Database")
root.geometry("400x160")
root.resizable(width=False, height=False)
connectFrame = tk.Frame()
connectFrame.pack()
# Defining Functions

def unhidePassword():
if (checked.get()):
passwordEntry.configure(show="")
elif (not checked.get()):
passwordEntry.configure(show="*")

def createConnection():
try:
global db
db = mysql.connector.connect(
user=user.get(),
host=host.get(),
password=password.get(),
database=database.get(),
auth_plugin='mysql_native_password'
)
tkinter.messagebox.showinfo(message="Connection Created Successfully")
except mysql.connector.errors.ProgrammingError:
tkinter.messagebox.showerror(
message="Incorrect Data Entered")

# Creating Widgets
# introLabel = tk.Label(connectFrame, text="Connect To Database",
#                      padx = 15, pady = 10, bg = "#42caff")

userName_label = tk.Label(connectFrame, text="User Name: ")
user = tk.StringVar()
userName_entry = tk.Entry(connectFrame, bd=1, width=27, textvariable=user)
hostLabel = tk.Label(connectFrame, text="Host: ")
host = tk.StringVar()
hostEntry = tk.Entry(connectFrame, bd=1, width=27, textvariable=host)

passwordLabel = tk.Label(connectFrame, text="Password: ")
password = tk.StringVar()
passwordEntry = tk.Entry(connectFrame, bd=1, width=27, textvariable=password)
checked = tk.IntVar()  # For checking if check button is checked or not
showPass = tk.Checkbutton(connectFrame, variable=checked,
text="Show Password", command=unhidePassword)

dataBaseLabel = tk.Label(connectFrame, text="Database:  ")
database = tk.StringVar()
dataBaseEntry = tk.Entry(connectFrame, bd=1, width=27, textvariable=database)
connectBtn = tk.Button(
connectFrame, text="Connect To Database", cursor="hand2", bd=0, bg="#0ffcdd", command=lambda: createConnection())
curosr = db.cursor()
curosr.execute("SELECT * FROM visitors")
print(curosr.fetchall())

userName_label.grid(row=0, column=0)
userName_entry.grid(row=0, column=1)
hostLabel.grid(row=1, column=0)
hostEntry.grid(row=1, column=1)
passwordLabel.grid(row=2, column=0)
passwordEntry.grid(row=2, column=1)
passwordEntry.configure(show="*")
showPass.grid(row=2, column=2, ipadx=20)
dataBaseLabel.grid(row=4, column=0)
dataBaseEntry.grid(row=4, column=1)
connectBtn.grid(row=7, column=1, pady=15, ipady=5)

root.mainloop()

已尝试将返回的对象声明为全局对象，但仍然显示未定义的错误。但是，我的编辑器能够访问方法和属性。谁能解释这是什么？

Answer 1

为了运行您的脚本，我做了一些更改。

• 导入 MySQLdb 作为 mdb
• 导入系统

所以你的脚本看起来像

import tkinter as tk
import MySQLdb as mdb
import tkinter.messagebox
import sys
root = tk.Tk()
root.title("Login To Database")
root.geometry("400x160")
root.resizable(width=False, height=False)

connectFrame = tk.Frame()
connectFrame.pack()
# Defining Functions

def unhidePassword():
if (checked.get()):
passwordEntry.configure(show="")
elif (not checked.get()):
passwordEntry.configure(show="*")

def createConnection():
try:
global db
db = mdb.connect(
user=user.get(),
host=host.get(),
password=password.get(),
database=database.get(),
auth_plugin='mysql_native_password'
)
tkinter.messagebox.showinfo(message="Connection Created Successfully")
except :
msg = (sys.exc_info()[1],
sys.exc_info()[0],
sys.modules[__name__])
print(msg)
#tkinter.messagebox.showerror(msg)

# Creating Widgets
# introLabel = tk.Label(connectFrame, text="Connect To Database",
#                      padx = 15, pady = 10, bg = "#42caff")

userName_label = tk.Label(connectFrame, text="User Name: ")
user = tk.StringVar()
userName_entry = tk.Entry(connectFrame, bd=1, width=27, textvariable=user)
hostLabel = tk.Label(connectFrame, text="Host: ")
host = tk.StringVar()
hostEntry = tk.Entry(connectFrame, bd=1, width=27, textvariable=host)

passwordLabel = tk.Label(connectFrame, text="Password: ")
password = tk.StringVar()
passwordEntry = tk.Entry(connectFrame, bd=1, width=27, textvariable=password)
checked = tk.IntVar()  # For checking if check button is checked or not
showPass = tk.Checkbutton(connectFrame, variable=checked,
text="Show Password", command=unhidePassword)

dataBaseLabel = tk.Label(connectFrame, text="Database:  ")
database = tk.StringVar()
dataBaseEntry = tk.Entry(connectFrame, bd=1, width=27, textvariable=database)
connectBtn = tk.Button(connectFrame, text="Connect To Database", cursor="hand2", bd=0, bg="#0ffcdd", command=lambda: createConnection())


userName_label.grid(row=0, column=0)
userName_entry.grid(row=0, column=1)
hostLabel.grid(row=1, column=0)
hostEntry.grid(row=1, column=1)
passwordLabel.grid(row=2, column=0)
passwordEntry.grid(row=2, column=1)
passwordEntry.configure(show="*")
showPass.grid(row=2, column=2, ipadx=20)
dataBaseLabel.grid(row=4, column=0)
dataBaseEntry.grid(row=4, column=1)
connectBtn.grid(row=7, column=1, pady=15, ipady=5)

root.mainloop()

因此，当您尝试连接时，您会看到 sys 报告的此错误

(TypeError("'auth_plugin' is an invalid keyword argument for connect()"), <class 'TypeError'>, <module '__main__' (built-in)>)

如果删除此行

auth_plugin='mysql_native_password'

脚本应该可以工作。

但是，这不是做您想做的事的正确方法。