[英]Can I get table names along with column names using .description() in Python's DB API?
[英]Why can't I use variables (using “%s” or “?”) to refer to table and column names in sqlite's “CREATE TABLE IF NOT EXISTS” and “INSERT INTO VALUES”?
我正在为我的应用程序创建一个数据库 class,因为我在各种场合都需要数据库表。 我正在使用 sqlite3,我需要我的代码尽可能通用,但是当我使用“%s”和/或“?”时对于表名和列标题,我得到了上述错误。
这是我的代码:
import sqlite3
conn = sqlite3.connect("cows.db")
c = conn.cursor()
class databases:
global c
def __init__(self, table_name):
self.table_name = table_name
def create_table(self, *args, **kwargs):
c.execute('CREATE TABLE IF NOT EXISTS %s(%s)', (self.table_name, args))
c.execute("INSERT INTO %s VALUES (%s)", (self.table_name, kwargs))
conn.commit()
def delete_record(self, *args):
c.execute(''' DELETE FROM ? WHERE ? = ?''', (self.table_name, args))
conn.commit()
cows = databases('cow')
cows.create_table('cow_id REAL', 'lactation_phase TEXT', 'milk_production REAL', 'weight REAL')
这是错误消息:
C:\Users\farid\PycharmProjects\cownutritionmanagmentsystem\venv\Scripts\python.exe C:/Users/farid/PycharmProjects/cownutritionmanagmentsystem/database.py
Traceback (most recent call last):
File "C:/Users/farid/PycharmProjects/cownutritionmanagmentsystem/database.py", line 24, in <module>
cows.create_table('cow_id REAL', 'lactation_phase TEXT', 'milk_production REAL', 'weight REAL')
File "C:/Users/farid/PycharmProjects/cownutritionmanagmentsystem/database.py", line 14, in create_table
c.execute('CREATE TABLE IF NOT EXISTS %s(%s)', (self.table_name, args))
sqlite3.OperationalError: near "%": syntax error
您可以使用%s
来引用字符串中的表名或其他变量。 注意%s
标记插入字符串, %d
标记插入 integer。
或者,您也可以使用format
方法替换字符串中变量的值。 在format
方法中,花括号显示插入值应在 go 的位置。 您可以使用此方法插入多个值,值不必只是字符串,也可以是数字和其他 Python 对象。
import sqlite3
conn = sqlite3.connect("cows.db")
c = conn.cursor()
class databases:
global c
def __init__(self, table_name):
self.table_name = table_name
def create_table(self, *args, **kwargs):
c.execute('CREATE TABLE IF NOT EXISTS %s(%s)' % (self.table_name, args))
c.execute("INSERT INTO %s VALUES (%s)" % (self.table_name, kwargs)) # Notice how we have used % operator here
conn.commit()
def delete_record(self, *args):
c.execute(''' DELETE FROM {} WHERE {} = {}'''.format(self.table_name, args)) # We have used format method here
conn.commit()
cows = databases('cow')
cows.create_table('cow_id REAL', 'lactation_phase TEXT', 'milk_production REAL', 'weight REAL')
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