python 常见面试题整理（1）

导出mongo数据过程记录

mongoexport

# 直接从某个表导出期望字段，生成CSV
mongoexport --host 127.0.0.1 --db sampleData --collection eventV4 --csv --out events.csv --fields '_id,something'

# 增加一个检索filter后导出CSV
mongoexport --host 127.0.0.1 --db sampleData --collection eventV4 --queryFile ./range.json --csv --out events.csv --fields '_id,something'

# cat range.json
{"something":{"$gt":1}}

参数

Usage:
  mongoexport <options>

Export data from MongoDB in CSV or JSON format.

See http://docs.mongodb.org/manual/reference/program/mongoexport/ for more information.

general options:
      --help                     print usage
      --version                  print the tool version and exit

verbosity options:
  -v, --verbose                  more detailed log output (include multiple times for more verbosity, e.g. -vvvvv)
      --quiet                    hide all log output

connection options:
  -h, --host=                    mongodb host to connect to (setname/host1,host2 for replica sets)
      --port=                    server port (can also use --host hostname:port)

authentication options:
  -u, --username=                username for authentication
  -p, --password=                password for authentication
      --authenticationDatabase=  database that holds the user's credentials
      --authenticationMechanism= authentication mechanism to use

namespace options:
  -d, --db=                      database to use
  -c, --collection=              collection to use

output options:
  -f, --fields=                  comma separated list of field names (required for exporting CSV) e.g. -f "name,age"
      --fieldFile=               file with field names - 1 per line
      --type=                    the output format, either json or csv (defaults to 'json')
  -o, --out=                     output file; if not specified, stdout is used
      --jsonArray                output to a JSON array rather than one object per line
      --pretty                   output JSON formatted to be human-readable

querying options:
  -q, --query=                   query filter, as a JSON string, e.g., '{x:{$gt:1}}'
  -k, --slaveOk                  allow secondary reads if available (default true)
      --forceTableScan           force a table scan (do not use $snapshot)
      --skip=                    number of documents to skip
      --limit=                   limit the number of documents to export
      --sort=                    sort order, as a JSON string, e.g. '{x:1}'

部分参数说明：

-h:指明数据库宿主机的IP  
-u:指明数据库的用户名
-p:指明数据库的密码
-d:指明数据库的名字
-c:指明collection的名字
-f:指明要导入那些列
-- limit 导出的行数
-- skip 从第几行开始导出
-- sort 排序之类的

mongoexport

对应导出工具，使用上基本和mongoexport差不多。想具体了解如何使用的请戳这里

总结

使用下来比较简单没出什么幺蛾子！！！