python - 通过数据库的另一个函数调用函数中的变量

Question

我尝试在 python 中应用 Don't Repeat Yourself 概念。

import sqlite3



# Start connection and create cursor
def startdb():
    # 1. Create connection
    conn = sqlite3.connect("books.db")
    # 2. Create a cursor object
    cur = conn.cursor()

# Commit and close db
def closedb():
    # 4. Commit changes
    conn.commit()
    # 5. Close connections
    conn.close()

# Connect python to db
def connect():
    startdb()
    # 3. Create table if does not exist
    cur.execute("CREATE TABLE IF NOT EXISTS book (id INTEGER PRIMARY KEY, title text, author text, year integer, isbn integer)")
    closedb()

# Insert data to db
def insert(title,author,year,isbn):
    startdb()
    # SQL queries to insert
    cur.execute("INSERT INTO book VALUES (NULL,?,?,?,?)",(title,author,year,isbn))
    closedb()

# View all datas
def view():
    startdb()
    cur.execute("SELECT * FROM book")
    rows=cur.fetchall()
    conn.close()
    return rows



connect()
insert("The sea","John Tablet",1983,913123132)
print(view())

显然我遇到了名称错误

Traceback (most recent call last):
  File "backend.py", line 45, in <module>
    connect()
  File "backend.py", line 25, in connect
    cur.execute("CREATE TABLE IF NOT EXISTS b
ook (id INTEGER PRIMARY KEY, title text, auth
or text, isbn integer)")

NameError: name 'cur' is not defined

根据我的理解，这意味着startdb()函数没有传入变量conn和cur

根据我的搜索，我需要使用一个带有 __init__ 函数的类，是否有更好的解决方案来使用 startdb() 和 closedb() 函数？

Answer 1

如@juanpa.arrivillaga 所述，您需要一个全局声明。 你在 sqlite3 查询中犯了一个错误，你忘记了 SQL 创建表查询中的年份列

import sqlite3



# Start connection and create cursor
def startdb():
    global conn, cur
    # 1. Create connection
    conn = sqlite3.connect("books.db")
    # 2. Create a cursor object
    cur = conn.cursor()

# Commit and close db
def closedb():
    # 4. Commit changes
    conn.commit()
    # 5. Close connections
    conn.close()

# Connect python to db
def connect():
    startdb()
    # 3. Create table if does not exist
    cur.execute("CREATE TABLE IF NOT EXISTS book (id INTEGER PRIMARY KEY, title text, author text,year integer, isbn integer)")
    closedb()

# Insert data to db
def insert(title,author,year,isbn):
    startdb()
    # SQL queries to insert
    cur.execute("INSERT INTO book VALUES (NULL,?,?,?,?)",(title,author,year,isbn))
    closedb()

# View all datas
def view():
    startdb()
    cur.execute("SELECT * FROM book")
    rows=cur.fetchall()
    conn.close()
    return rows



connect()
insert("The sea","John Tablet",1983,913123132)
print(view())