Question

我有一个如下列表：

import subprocess

last_logins = [i.split(' ', 1)[0] for i in subprocess.check_output('last').split('\n') if 'reboot' not in i]
print("The last five logins were: {0}".format(', '.join(last_logins[0:5])))

它返回：

The last five logins were: vagrant, vagrant, vagrant, vagrant, vagrant

如何嵌套保持用户记录的子循环，在这种情况下，返回：

The last five logins were: vagrant: 2x, some_other_user: 3x

是的，它很难看，理解线太长了。（我对编写更清晰的代码的批评/建议持开放态度）。但我也想找到在（列表）理解中嵌套循环的正确方法。

Answer 1

我认为您正在寻找collections.Counter()：

from collections import Counter

last_logins = ['Vagrant', 'Vagrant', 'Some Other User', 'Vagrant', 'Some Other User']

last_five_stats = Counter(last_logins[:5])
print("The last five logins were: {0}".format(', '.join("{0}: {1}x".format(user, count) for user, count in last_five_stats.items())))

打印：

The last five logins were: Vagrant: 3x, Some Other User: 2x

这对f-strings（Python 3.6 +）来说会更好一些：

last_five_stats = (f"{user}: {count}x" for user, count in Counter(last_logins[:5]).items())
print(f"The last five logins were: {', '.join(last_five_stats)}")

如何嵌套列表理解

1 个答案: