Implementation example of Python reading TXT file data and storing it in the built-in database (SQLite3)

This article mainly introduces the method of Python to read TXT file data and store it into the built-in database SQLite3. It involves Python's reading of txt files and the creation, insertion, query and other related operation skills of sqlite3 database. Friends who need it can Refer to the following

The example of this article describes the method of reading TXT file data in Python and storing it in the built-in database SQLite3. Share it with everyone for your reference, the details are as follows:

When the TXT file is too large and the computer memory is not enough, we can choose to read the TXT file line by line and store it into Python's built-in lightweight splite database. This can speed up the reading of data. When we need to read data repeatedly, the time savings brought by this speed increase are very considerable. For example, when we are training data, we need to iterate 100,000 times, that is, Reading from a file 100,000 times, even if it only speeds up by 0.1 seconds each time, can save several hours of time.

#创建数据库并把txt文件的数据存进数据库
import sqlite3      #导入sqlite3
cx = sqlite3.connect('./train.db')  #创建数据库，如果数据库已经存在，则链接数据库；如果数据库不存在，则先创建数据库，再链接该数据库。
cu = cx.cursor()           #定义一个游标，以便获得查询对象。
cu.execute('create table if not exists train4 (id integer primary key,name text)')  #创建表
fr = open('data_sample.txt')    #打开要读取的txt文件
i = 0
for line in fr.readlines():    #将数据按行插入数据库的表train4中。
  cu.execute('insert into train4 values(?,?)',(i,line))
  i +=1
cu.close()   #关闭游标
cx.commit()   #事务提交
cx.close()   #关闭数据库

Query data:

cu.execute('select * from train4 where id = ?',(i,)) #i代表你要读取表train4中某一行的数据
result = cu.fetchall()

Note: If it has been closed previously If the database is closed, you must reopen the database and create a cursor when querying. Pay attention to this.

The complete query program is like this:

import sqlite3
cx = sqlite3.connect('./train.db')
cu = cx.cursor()
for i in range(5):
  cu.execute('select * from train4 where id = ?',(i,))
  result = cu.fetchall()
  cx.commit()
cu.close()
cx.close()

Another: Here is another SQLite3 data operation for everyone Class for your reference:

import sqlite3
# ***************************************************
# *
# * Description: Python操作SQLite3数据库辅助类(查询构造器)
# * Author: wangye
# *
# ***************************************************
def _wrap_value(value):
  return repr(value)
def _wrap_values(values):
  return list(map(_wrap_value, values))
def _wrap_fields(fields):
  for key,value in fields.items():
    fields[key] = _wrap_value(value)
  return fields
def _concat_keys(keys):
  return "[" + "],[".join(keys) + "]"
def _concat_values(values):
  return ",".join(values)
def _concat_fields(fields, operator = (None, ",")):
  if operator:
    unit_operator, group_operator = operator
  # fields = _wrap_fields(fields)
  compiled = []
  for key,value in fields.items():
    compiled.append("[" + key + "]")
    if unit_operator:
      compiled.append(unit_operator)
      compiled.append(value)
    compiled.append(group_operator)
  compiled.pop() # pop last group_operator
  return " ".join(compiled)
class DataCondition(object):
  """
    本类用于操作SQL构造器辅助类的条件语句部分
    例如:
    DataCondition(("=", "AND"), id = 26)
    DataCondition(("=", "AND"), True, id = 26)
  """
  def __init__(self, operator = ("=", "AND"), ingroup = True, **kwargs):
    """
      构造方法
      参数:
        operator 操作符，分为(表达式操作符, 条件运算符)
        ingroup 是否分组，如果分组，将以括号包含
        kwargs  键值元组，包含数据库表的列名以及值
             注意这里的等于号不等于实际生成SQL语句符号
             实际符号是由operator[0]控制的
      例如:
      DataCondition(("=", "AND"), id = 26)
      (id=26)
      DataCondition((">", "OR"), id = 26, age = 35)
      (id>26 OR age>35)
      DataCondition(("LIKE", "OR"), False, name = "John", company = "Google")
      name LIKE 'John' OR company LIKE "Google"
    """
    self.ingroup = ingroup
    self.fields = kwargs
    self.operator = operator
  def __unicode__(self):
    self.fields = _wrap_fields(self.fields)
    result = _concat_fields(self.fields, self.operator)
    if self.ingroup:
      return "(" + result + ")"
    return result
  def __str__(self):
    return self.__unicode__()
  def toString(self):
    return self.__unicode__()
class DataHelper(object):
  """
    SQLite3 数据查询辅助类
  """
  def __init__(self, filename):
    """
      构造方法
      参数: filename 为SQLite3 数据库文件名
    """
    self.file_name = filename
  def open(self):
    """
      打开数据库并设置游标
    """
    self.connection = sqlite3.connect(self.file_name)
    self.cursor = self.connection.cursor()
    return self
  def close(self):
    """
      关闭数据库，注意若不显式调用此方法，
      在类被回收时也会尝试调用
    """
    if hasattr(self, "connection") and self.connection:
      self.connection.close()
  def __del__(self):
    """
      析构方法，做一些清理工作
    """
    self.close()
  def commit(self):
    """
      提交事务
      SELECT语句不需要此操作，默认的execute方法的
      commit_at_once设为True会隐式调用此方法，
      否则就需要显示调用本方法。
    """
    self.connection.commit()
  def execute(self, sql = None, commit_at_once = True):
    """
      执行SQL语句
      参数:
        sql 要执行的SQL语句，若为None，则调用构造器生成的SQL语句。
        commit_at_once 是否立即提交事务，如果不立即提交，
        对于非查询操作，则需要调用commit显式提交。
    """
    if not sql:
      sql = self.sql
    self.cursor.execute(sql)
    if commit_at_once:
      self.commit()
  def fetchone(self, sql = None):
    """
      取一条记录
    """
    self.execute(sql, False)
    return self.cursor.fetchone()
  def fetchall(self, sql = None):
    """
      取所有记录
    """
    self.execute(sql, False)
    return self.cursor.fetchall()
  def __concat_keys(self, keys):
    return _concat_keys(keys)
  def __concat_values(self, values):
    return _concat_values(values)
  def table(self, *args):
    """
      设置查询的表，多个表名用逗号分隔
    """
    self.tables = args
    self.tables_snippet = self.__concat_keys(self.tables)
    return self
  def __wrap_value(self, value):
    return _wrap_value(value)
  def __wrap_values(self, values):
    return _wrap_values(values)
  def __wrap_fields(self, fields):
    return _wrap_fields(fields)
  def __where(self):
    # self.condition_snippet
    if hasattr(self, "condition_snippet"):
      self.where_snippet = " WHERE " + self.condition_snippet
  def __select(self):
    template = "SELECT %(keys)s FROM %(tables)s"
    body_snippet_fields = {
      "tables" : self.tables_snippet,
      "keys" : self.__concat_keys(self.body_keys), 
    }
    self.sql = template % body_snippet_fields
  def __insert(self):
    template = "INSERT INTO %(tables)s (%(keys)s) VALUES (%(values)s)"
    body_snippet_fields = {
      "tables" : self.tables_snippet,
      "keys" : self.__concat_keys(list(self.body_fields.keys())),
      "values" : self.__concat_values(list(self.body_fields.values()))
    }
    self.sql = template % body_snippet_fields
  def __update(self):
    template = "UPDATE %(tables)s SET %(fields)s"
    body_snippet_fields = {
      "tables" : self.tables_snippet,
      "fields" : _concat_fields(self.body_fields, ("=",","))
    }
    self.sql = template % body_snippet_fields
  def __delete(self):
    template = "DELETE FROM %(tables)s"
    body_snippet_fields = {
      "tables" : self.tables_snippet
    }
    self.sql = template % body_snippet_fields
  def __build(self):
    {
      "SELECT": self.__select,
      "INSERT": self.__insert,
      "UPDATE": self.__update,
      "DELETE": self.__delete
    }[self.current_token]()
  def __unicode__(self):
    return self.sql
  def __str__(self):
    return self.__unicode__()
  def select(self, *args):
    self.current_token = "SELECT"
    self.body_keys = args
    self.__build()
    return self
  def insert(self, **kwargs):
    self.current_token = "INSERT"
    self.body_fields = self.__wrap_fields(kwargs)
    self.__build()
    return self
  def update(self, **kwargs):
    self.current_token = "UPDATE"
    self.body_fields = self.__wrap_fields(kwargs)
    self.__build()
    return self
  def delete(self, *conditions):
    self.current_token = "DELETE"
    self.__build()
    #if *conditions:
    self.where(*conditions)
    return self
  def where(self, *conditions):
    conditions = list(map(str, conditions))
    self.condition_snippet = " AND ".join(conditions)
    self.__where()
    if hasattr(self, "where_snippet"):
      self.sql += self.where_snippet
    return self

The above is the detailed content of Implementation example of Python reading TXT file data and storing it in the built-in database (SQLite3). For more information, please follow other related articles on the PHP Chinese website!