Python csv错误：序列预期

发布时间：2020-12-20 11:34:38 所属栏目：Python 来源：网络整理

导读：我使用psycopg2连接 postgresql和 python,这是我的脚本, import sys#set up psycopg2 environmentimport psycopg2#driving_distance modulequery = """ select * from driving_distance ($$ select gid as id,start_id::int4 as source,end_id::int4 as targ

我使用psycopg2连接 postgresql和 python,这是我的脚本,

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
    )
"""

#make connection between python and postgresql
conn = psycopg2.connect("dbname = 'TC_routing' 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

h = 0
ars = []
element = list(rs)
while h <= 15:
    rp = element[0][h][2]
    ars.append(rp)
    h = h + 1

print ars
conn.close()

输出很好,

[0.0,11810.7956476379,16018.6818979217,18192.3576530232,21507.7366792666,25819.1955059578,26331.2523709618,49447.0908955008,28807.7871013087,39670.8579371438,42723.0239515299,38719.7320396044,38265.4435766971,40744.8813155033,43770.2158657742,46224.8748774639]

但如果我在下面添加一些行以将结果导出到csv文件,我收到此错误,

import csv

with open('test.csv','wb') as f:
    writer = csv.writer(f,delimiter = ',')
    for row in ars:
        writer.writerow(row)

[0.0,46224.8748774639]

Traceback (most recent call last):
  File "C:/Users/Heinz/Desktop/python_test/distMatrix_test.py",line 54,in <module>
    writer.writerow(row)
Error: sequence expected

如何解决这个问题？

我在Windows 8.1 x64下使用python 2.7.6和pyscripter.随便给我任何建议,非常感谢！

解决方法

import csv

  with open('test.csv','wb') as f:
     writer = csv.writer(f,')
     for row in ars:
         writer.writerow(row)

ars只是一个列表.所以你的for循环不会从ars中提取一行.它从ars列表中获取一个元素,并尝试将其写为一行.

尝试替换它

for row in ars:
         writer.writerow([row])

这会将每个元素写成csv文件中的一行.

或者如果你想在输出中有一行,那么就不要使用for循环,而是使用

writer.writerow(ars)

（编辑：李大同）

【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容!