How to save results of postgresql to csv/excel file using psycopg2?
我在postgresql中使用driving_distance来查找所有节点之间的距离,这是我在pyscripter中的python脚本,
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 | import sys #set up psycopg2 environment import psycopg2 #driving_distance module query =""" select * from driving_distance ($$ select gid as id, start_id::int4 as source, end_id::int4 as target, shape_leng::double precision as cost from network $$, %s, %s, %s, %s ) ;""" #make connection BETWEEN python AND postgresql conn = psycopg2.connect("dbname = 'routing_template' user = 'postgres' host = 'localhost' password = '****'") cur = conn.cursor() #count ROWS IN the TABLE cur.execute("select count(*) from network") RESULT = cur.fetchone() k = RESULT[0] + 1 #run loops rs = [] i = 1 while i <= k: cur.execute(query, (i, 1000000, FALSE, FALSE)) rs.append(cur.fetchall()) i = i + 1 #print RESULT FOR record IN rs: print record conn.close() |
结果很好,python解释器中的部分内容如下所示,
1 2 | [(1, 2, 35789.4069722436), (2, 2, 31060.0761437413), (3, 19, 30915.1312550546), (4, 3, 33438.0715007666), (5, 4, 29149.0894812718), (6, 7, 25504.020006665), (7, 7, 29594.741802956), (8, 5, 20736.2427352646), (9, 10, 19545.809601197), (10, 8, 22609.5146670393), (11, 9, 14134.5400189648), (12, 11, 12266.7845493204), (13, 18, 17426.7449057031), (14, 21, 11754.7277029158), (15, 18, 13128.3548040769), (16, 20, 21924.2253916803), (17, 11, 15209.9969992088), (18, 20, 26316.7797545076), (19, 13, 604.414419026164), (20, 16, 740.652673783403), (21, 15, 0.0), (22, 15, 2378.768084459)] [(1, 2, 38168.1750567026), (2, 2, 33438.8442282003), (3, 19, 33293.8993395136), (4, 3, 35816.8395852256), (5, 4, 31527.8575657308), (6, 7, 27882.788091124), (7, 7, 31973.509887415), (8, 5, 23115.0108197236), (9, 10, 21924.577685656), (10, 8, 24988.2827514983), (11, 9, 16513.3081034238), (12, 11, 14645.5526337793), (13, 18, 19805.5129901621), (14, 21, 14133.4957873748), (15, 18, 15507.1228885359), (16, 20, 24302.9934761393), (17, 11, 17588.7650836678), (18, 20, 28695.5478389666), (19, 13, 2983.18250348516), (20, 16, 3119.4207582424), (21, 15, 2378.768084459), (22, 15, 0.0)] |
我想将这些结果导出到新的csv或excel文件,我看过这些相关的帖子和网站,
- PostgreSQL:将结果数据从SQL查询导出到Excel / CSV
- 将(postgres)sql输出保存到csv文件
- Psycopg 2.5.3.dev0文档
但仍然无法将这些工作输出到pyscripter下,我该怎么办?
我正在使用Windows 8.1 x64下的postgresql 8.4,python 2.7.6。
更新#1:
我尝试了Talvalin提供的以下代码(谢谢!),
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 | import sys #set up psycopg2 environment import psycopg2 #driving_distance module query =""" select * from driving_distance ($$ select gid as id, start_id::int4 as source, end_id::int4 as target, shape_leng::double precision as cost from network $$, %s, %s, %s, %s ) """ #make connection BETWEEN python AND postgresql conn = psycopg2.connect("dbname = 'TC_routing' user = 'postgres' host = 'localhost' password = '****'") cur = conn.cursor() outputquery = 'copy ({0}) to stdout with csv header'.format(query) WITH OPEN('resultsfile', 'w') AS f: cur.copy_expert(outputquery, f) conn.close() |
但是下面有错误,
1 2 3 4 5 6 7 8 | >>> Traceback (most recent CALL LAST): File"C:/Users/Heinz/Desktop/python_test/driving_distance_loop_test.py", line 27, IN <module> cur.copy_expert(outputquery, f) ProgrammingError: 錯誤: 在"語法錯誤"附近發生 % LINE 10: $$, %s, %s, %s, %s ^ |
也许我需要在上面的代码中添加更多内容。
基于Psycopg2的cursor.copy_expert()和Postgres COPY文档以及您的原始代码示例,请试一试。 我在笔记本电脑上测试了类似的查询导出,所以我有理由相信这应该有用,但如果有任何问题请告诉我。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 | import sys #set up psycopg2 environment import psycopg2 #driving_distance module #note the lack OF TRAILING semi-colon IN the query string, AS per the Postgres documentation query =""" select * from driving_distance ($$ select gid as id, start_id::int4 as source, end_id::int4 as target, shape_leng::double precision as cost from network $$, %s, %s, %s, %s ) """ #make connection BETWEEN python AND postgresql conn = psycopg2.connect("dbname = 'routing_template' user = 'postgres' host = 'localhost' password = 'xxxx'") cur = conn.cursor() outputquery ="COPY ({0}) TO STDOUT WITH CSV HEADER".format(query) WITH OPEN('resultsfile', 'w') AS f: cur.copy_expert(outputquery, f) conn.close() |