如何使用python从postgresql中选择一个没有[(100)，]的像100这样的数据

Question

我有一个只有1行的表，我只需要更新第一行的数据。我需要在初创公司预览数据，比如总财富：-2000现金：-0储蓄：-2000。但它的预览如下所示。在这里输入图片描述，所以请给我一个解决方案。

from tkinter import *
import psycopg2
try:
connection = psycopg2.connect(user="postgres",
password="postgres",
host="localhost",
port="5432",
database="money_db")
cursor = connection.cursor()
query_cash = "select cash from main where index = 1;"
query_savings = "select savings from main where index = 1;"
cursor.execute(query_cash)
cash = cursor.fetchall()

cursor.execute(query_savings)
savings = cursor.fetchall()

t_w = (cash + savings)
cursor.execute("commit;")
if (connection):
cursor.close()
connection.close()
print("PostgreSQL connection is closed")
except (Exception, psycopg2.Error) as error:
print("Error while fetching data from PostgreSQL", error)
root = Tk()
root.geometry("900x500")
root.resizable(width=False, height=False)
t_w_lbl = Label(text="Total Wealth = " + str(t_w), font=("Calibry", 14), bg="white")
t_w_lbl.place(rely=0.04, relx=0.1)
cash_lbl = Label(text="Cash = " + str(cash), font=("Calibry", 14), bg="white")
cash_lbl.place(rely=0.04, relx=0.45)
photo = PhotoImage(file = "exchange.png")
exchange_btn = Button(image = photo, command = lambda: exchange())
exchange_btn.place(relx = 0.64, rely = 0.03, height = 35, width = 50)
savings_lbl = Label(text="Savings = " + str(savings), font=("Calibry", 14), bg="white")
savings_lbl.place(rely=0.04, relx=0.8)`

Answer 1

您应该使用fetchone方法，并解压缩返回的元组(注意添加的逗号(。

更改：

cash = cursor.fetchall()
...
savings = cursor.fetchall()

至：

cash, = cursor.fetchone()
...
savings, = cursor.fetchone()