从Python中的SQL类型地理列绘制面

如何解决从Python中的SQL类型地理列绘制面

我有一个Sqlite数据库，其表包含一个geo列。当我将此表作为图层添加到QGIS中时，它将显示带有多边形的Chicago地图，如下所示。我认为，多边形点存储在名为geo的列中。

我正在尝试在Python中绘制相同内容，以便能够使用Matplotlib在此布局之上添加更多内容。首先，我可以使用以下代码（我写的）在Python中加载名为“ Zone”的表：

import sqlite3  # Package for SQLite
### BEGIN DEFINING A READER FUNCTION ###
def Conditional_Sqdb_reader(Sqdb,Tablename,Columns,Condition):
    conn = sqlite3.connect(Sqdb) # Connects the file to Python
    print("\nConnected to %s.\n"%(Sqdb))
    conn.execute('pragma foreign_keys = off') # Allows making changes into the SQLite file
    print("SQLite Foreign_keys are unlocked...\n")
    c = conn.cursor() # Assigns c as the cursor
    print("Importing columns: %s \nin table %s from %s.\n"%(Columns,Sqdb))
    c.execute('''SELECT {columns} 
                 FROM {table}
                 {condition}'''.format(table=Tablename,columns=Columns,condition=Condition)) # Selects the table to read/fetch
    Sql_headers = [description[0] for description in c.description]
    Sql_columns = c.fetchall() # Reads the table and saves into the memory as Sql_rows
    print("Importing completed...\n")
    conn.commit() # Commits all the changes made
    conn.execute('pragma foreign_keys = on') # Locks the SQLite file
    print("SQLite Foreign_keys are locked...\n")
    conn.close() # Closes the SQLite file
    print("Disconnected from %s.\n"%(Sqdb))
    return Sql_headers,Sql_columns
### END DEFINING A READER FUNCTION ###

Sqdb = '/mypath/myfile.sqlite'
Tablename = "Zone" # Change this with your desired table to play with
Columns = """*""" # Changes this with your desired columns to import
Condition = ''    # Add your condition and leave blank if no condition

headings,data = Conditional_Sqdb_reader(Sqdb,Condition)

表中的数据作为列表存储在“数据”中。因此，data[0][-1]产生第一行多边形的地理，看起来像：b'\x00\x01$i\x00\x00@\xd9\x94\x8b\xd6<\x1bAb\xda7\xb6]\xb1QA\xf0\xf7\x8b\x19UC\x1bA\x9c\xde\xc5\r\xc3\xb1QA|\x03\x00\x00\x00\x01\x00\x00\x00\x06\x00\x00\x00Hlw\xef-C\x1bA\x9c\xde\xc5\r\xc3\xb1QA\xf0\xf7\x8b\x19UC\x1bAv\xc0u)^\xb1QA\xbcw\xd4\x88\xf1<\x1bAb\xda7\xb6]\xb1QA\xa5\xdc}n\xd7<\x1bA\x84.\xe1r\xbe\xb1QA@\xd9\x94\x8b\xd6<\x1bA\xce\x8eT\xef\xc1\xb1QAHlw\xef-C\x1bA\x9c\xde\xc5\r\xc3\xb1QA\xfe'我不知道如何解码并将其转换为有意义的一系列点，但这就是它的含义。是的，并且QGIS显然可以轻松地做到这一点。我如何在Python中绘制所有这些多边形，同时又可以稍后在Matplotlib世界中添加其他内容？

解决方法

花了几个小时并学习了很多东西之后，我找到了解决方案。基本上，在here中，在sqlite3中使用mod_spatialite是关键。当我嵌入此程序包时，它使我可以使用诸如ST_As_Text之类的spacespaceite函数，该函数将sql二进制字符串转换为以POLYGON((....开头的字符串，这是一种geopanda类型条目。有大量资料说明如何绘制此类数据。本质上，这是我的代码（与我的问题中的代码比较）：

import sqlite3  # Package for SQLite
### BEGIN DEFINING A READER FUNCTION ###
def Conditional_Sqdb_reader(Sqdb,Tablename,Columns,Condition):
    conn = sqlite3.connect(Sqdb) # Connects the file to Python
    conn.enable_load_extension(True)
    #mod_spatialite (recommended)
    conn.execute('SELECT load_extension("mod_spatialite.so")')   
    conn.execute('SELECT InitSpatialMetaData(1);')  
    print("\nConnected to %s.\n"%(Sqdb))
    conn.execute('pragma foreign_keys = off') # Allows making changes into the SQLite file
    print("SQLite Foreign_keys are unlocked...\n")
    c = conn.cursor() # Assigns c as the cursor
    print("Importing columns: %s \nin table %s from %s.\n"%(Columns,Sqdb))
    c.execute('''SELECT {columns} 
                 FROM {table}
                 {condition}'''.format(table=Tablename,columns=Columns,condition=Condition)) # Selects the table to read/fetch
    Sql_headers = [description[0] for description in c.description]
    Sql_columns = c.fetchall() # Reads the table and saves into the memory as Sql_rows
    print("Importing completed...\n")
    conn.commit() # Commits all the changes made
    conn.execute('pragma foreign_keys = on') # Locks the SQLite file
    print("SQLite Foreign_keys are locked...\n")
    conn.close() # Closes the SQLite file
    print("Disconnected from %s.\n"%(Sqdb))
    return Sql_headers,Sql_columns
### END DEFINING A READER FUNCTION ###

Sqdb = '/Users/tanercokyasar/Desktop/Qgis/chicago2018-Supply.sqlite'
Tablename = "Zone" # Change this with your desired table to play with
Columns = """*,ST_AsText(GEO) as GEO""" # Changes this with your desired columns to import
Condition = ''    # Add your condition and leave blank if no condition

headings,data = Conditional_Sqdb_reader(Sqdb,Condition)