Question

我正在用Python编写一些几乎可以工作的代码，但有一点我无法弄清楚。

我需要遍历2个列表。我想循环直到第一个列表完成;而第二个列表应该重复，直到第一个列表完成。

我想输入数据库列表和流列表。然后我希望代码通过替换“+ stream +”和“+ item +”的位置来输出9行。项目部分工作正常，但我不知道如何在迭代数据库列表时输出流列表。我希望流循环然后重复。所以它将从1a开始然后达到3c，然后再从1a开始。我希望这种情况发生，直到它到达列表中的最后一个数据库。

databases=input("Enter databases: ")
streams="1a 2a 3a 1b 2b 3b 1c 2c 3c"
stream="1a"

db_list = databases.split()
streams_list= streams.split()

for item in db_list:
    print("unlink $ORACLE_BASE/admin/" + item + "/backup")
    print("unlink $ORACLE_BASE/admin/" + item + "/dpdump")
    print("unlink $ORACLE_BASE/admin/" + item + "/exp")
    print("mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM" + stream + "/" + item + "/backup")
    print("mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM" + stream + "/" + item + "/dpdump")
    print("mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM" + stream + "/" + item + "/exp")
    print("ln -s $ORACLE_BASE/acfsmounts/global/STREAM" + stream + "/" + item + "/backup $ORACLE_BASE/admin/" + item + "/backup")
    print("ln -s $ORACLE_BASE/acfsmounts/global/STREAM" + stream + "/" + item + "/dpdump $ORACLE_BASE/admin/" + item + "/dpdump")
    print("ln -s $ORACLE_BASE/acfsmounts/global/STREAM" + stream + "/" + item + "/exp    $ORACLE_BASE/admin/" + item + "/exp")

这是输出：

Enter databases: database1 database2 database3
unlink $ORACLE_BASE/admin/database1/backup
unlink $ORACLE_BASE/admin/database1/dpdump
unlink $ORACLE_BASE/admin/database1/exp
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM1a/database1/backup
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM1a/database1/dpdump
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM1a/database1/exp
ln -s $ORACLE_BASE/acfsmounts/global/STREAM1a/database1/backup $ORACLE_BASE/admin/database1/backup
ln -s $ORACLE_BASE/acfsmounts/global/STREAM1a/database1/dpdump $ORACLE_BASE/admin/database1/dpdump
ln -s $ORACLE_BASE/acfsmounts/global/STREAM1a/database1/exp    $ORACLE_BASE/admin/database1/exp
unlink $ORACLE_BASE/admin/database2/backup
unlink $ORACLE_BASE/admin/database2/dpdump
unlink $ORACLE_BASE/admin/database2/exp
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM1a/database2/backup
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM1a/database2/dpdump
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM1a/database2/exp
ln -s $ORACLE_BASE/acfsmounts/global/STREAM1a/database2/backup $ORACLE_BASE/admin/database2/backup
ln -s $ORACLE_BASE/acfsmounts/global/STREAM1a/database2/dpdump $ORACLE_BASE/admin/database2/dpdump
ln -s $ORACLE_BASE/acfsmounts/global/STREAM1a/database2/exp    $ORACLE_BASE/admin/database2/exp
unlink $ORACLE_BASE/admin/database3/backup
unlink $ORACLE_BASE/admin/database3/dpdump
unlink $ORACLE_BASE/admin/database3/exp
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM1a/database3/backup
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM1a/database3/dpdump
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM1a/database3/exp
ln -s $ORACLE_BASE/acfsmounts/global/STREAM1a/database3/backup $ORACLE_BASE/admin/database3/backup
ln -s $ORACLE_BASE/acfsmounts/global/STREAM1a/database3/dpdump $ORACLE_BASE/admin/database3/dpdump
ln -s $ORACLE_BASE/acfsmounts/global/STREAM1a/database3/exp    $ORACLE_BASE/admin/database3/exp

我的输出每次都有STREAM1a，但我希望它循环通过1a，2a，3a，1b，2b，3b，1c，2c和3c的模式。如上所述，如果我有超过9个数据库，那么它将再次从1a开始。我怎样才能做到这一点？

我的代码中唯一没有按照我想要的方式运行的部分是“+ stream +”。

Answer 1

您应该使用itertools.cycle。这将允许您在无休止的重复循环中获取列表的元素。在循环开始时添加此代码：

stream_cycle = itertools.cycle(streams_list)
for item in db_list:
    stream = stream_cycle.next()

或@HughBothwell建议，您可以使用zip并将其包含在for循环的定义中：

for item, stream in zip(db_list, itertools.cycle(streams_list)):

无论哪种方式都会在循环的每次迭代中为您提供下一个流。如果你有比流更多的dbs，那么它会重复。

Answer 2

诀窍是使用名为itertools

的cycle中的迭代器

from itertools import cycle
databases=input("Enter databases: ")
streams="1a 2a 3a 1b 2b 3b 1c 2c 3c"
stream="1a"

db_list = databases.split()
stream_list= streams.split()

for item, stream in zip(db_list, cycle(stream_list)):
    print("unlink $ORACLE_BASE/admin/" + item + "/backup")
    print("unlink $ORACLE_BASE/admin/" + item + "/dpdump")
    print("unlink $ORACLE_BASE/admin/" + item + "/exp")
    print("mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM" + stream + "/" + item + "/backup")
    print("mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM" + stream + "/" + item + "/dpdump")
    print("mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM" + stream + "/" + item + "/exp")
    print("ln -s $ORACLE_BASE/acfsmounts/global/STREAM" + stream + "/" + item + "/backup $ORACLE_BASE/admin/" + item + "/backup")
    print("ln -s $ORACLE_BASE/acfsmounts/global/STREAM" + stream + "/" + item + "/dpdump $ORACLE_BASE/admin/" + item + "/dpdump")
    print("ln -s $ORACLE_BASE/acfsmounts/global/STREAM" + stream + "/" + item + "/exp    $ORACLE_BASE/admin/" + item + "/exp")

bonus - 使用docopt

解析命令行参数

小额奖励：让您调用脚本并方便地从命令行输入参数

安装docopt包（仅一次）

$ pip install docopt

编写修改后的脚本版本 db.py ：

"""Usage:
    db.py -s <stream> (-s <stream>)... <db> <db>...
    db.py -h

For all database names <db> generates commands combining it with
names of <stream>s.
"""
from docopt import docopt
from itertools import cycle   

args = docopt(__doc__)

db_list = args["<db>"]
stream_list = args["<stream>"]

for item, stream in zip(db_list, cycle(stream_list)):
    print("unlink $ORACLE_BASE/admin/" + item + "/backup")
    print("unlink $ORACLE_BASE/admin/" + item + "/dpdump")
    print("unlink $ORACLE_BASE/admin/" + item + "/exp")
    print("mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM" + stream + "/" + item + "/backup")
    print("mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM" + stream + "/" + item + "/dpdump")
    print("mkdir -p /oradba/app/oracle/acfsmounts/global/STREAM" + stream + "/" + item + "/exp")
    print("ln -s $ORACLE_BASE/acfsmounts/global/STREAM" + stream + "/" + item + "/backup $ORACLE_BASE/admin/" + item + "/backup")
    print("ln -s $ORACLE_BASE/acfsmounts/global/STREAM" + stream + "/" + item + "/dpdump $ORACLE_BASE/admin/" + item + "/dpdump")
    print("ln -s $ORACLE_BASE/acfsmounts/global/STREAM" + stream + "/" + item + "/exp    $ORACLE_BASE/admin/" + item + "/exp")

打印输出用法字符串：

$ python db.py
Usage:
    db.py -s <stream> (-s <stream>)... <db> <db>...
    db.py -h

显示一些帮助字符串：

$ python db.py -h
Usage:
    db.py -s <stream> (-s <stream>)... <db> <db>...
    db.py -h

For all database names <db> generates commands combining it with
names of <stream>s.

并将其称为实际使用：

$ python db.py -s s2 -s s2 db1 db2 db3
unlink $ORACLE_BASE/admin/db1/backup
unlink $ORACLE_BASE/admin/db1/dpdump
unlink $ORACLE_BASE/admin/db1/exp
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAMs2/db1/backup
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAMs2/db1/dpdump
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAMs2/db1/exp
ln -s $ORACLE_BASE/acfsmounts/global/STREAMs2/db1/backup $ORACLE_BASE/admin/db1/backup
ln -s $ORACLE_BASE/acfsmounts/global/STREAMs2/db1/dpdump $ORACLE_BASE/admin/db1/dpdump
ln -s $ORACLE_BASE/acfsmounts/global/STREAMs2/db1/exp    $ORACLE_BASE/admin/db1/exp
unlink $ORACLE_BASE/admin/db2/backup
unlink $ORACLE_BASE/admin/db2/dpdump
unlink $ORACLE_BASE/admin/db2/exp
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAMs2/db2/backup
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAMs2/db2/dpdump
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAMs2/db2/exp
ln -s $ORACLE_BASE/acfsmounts/global/STREAMs2/db2/backup $ORACLE_BASE/admin/db2/backup
ln -s $ORACLE_BASE/acfsmounts/global/STREAMs2/db2/dpdump $ORACLE_BASE/admin/db2/dpdump
ln -s $ORACLE_BASE/acfsmounts/global/STREAMs2/db2/exp    $ORACLE_BASE/admin/db2/exp
unlink $ORACLE_BASE/admin/db3/backup
unlink $ORACLE_BASE/admin/db3/dpdump
unlink $ORACLE_BASE/admin/db3/exp
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAMs2/db3/backup
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAMs2/db3/dpdump
mkdir -p /oradba/app/oracle/acfsmounts/global/STREAMs2/db3/exp
ln -s $ORACLE_BASE/acfsmounts/global/STREAMs2/db3/backup $ORACLE_BASE/admin/db3/backup
ln -s $ORACLE_BASE/acfsmounts/global/STREAMs2/db3/dpdump $ORACLE_BASE/admin/db3/dpdump
ln -s $ORACLE_BASE/acfsmounts/global/STREAMs2/db3/exp    $ORACLE_BASE/admin/db3/exp

Python循环遍历2个列表

2 个答案:

bonus - 使用docopt