问题描述
我正在尝试使用Python解决以下问题:
给出以下学生名单:
students = ['Tom','Kitty','Jessie','Chester','Curie','Darwing','Nancy','Sue','Peter','Andrew','Karren','Charles','Nikhil','Justin','Astha']
我需要将学生分为3组。每个学生的组身份由名为作业的列表中相同索引位置的整数指定:
assignment = [2,3,1,2,2]
使用理解,我需要生成以组号为关键字的字典,并以该组的学生列表为值。预期的输出是这样的:
{'Group 1': ['Chester','Charles'],'Group 2': ['Tom','Astha'],'Group 3': ['Kitty','Nikhil']}
zip(students,assignment)
我的逻辑是:检查每个元组中的整数(组号)。如果字典键中不存在该号码,请创建一个新号码,并添加与该组号码相对应的名称。如果存在,则将该值添加到字典的值列表中。
我想到了以下代码:
groupdict = {'Group{}'.format(group):[name] for name,group in zip(students,assignment) if group not in groupdict.keys()}
但是,它给了我以下结果:
{'Group 2': ['Astha'],'Group 3': ['Nikhil'],'Group 1': ['Charles']}
我试图包含else语句:
groupdict = {'Group{}'.format(group):[name] for name,assignment) if group not in groupdict.keys() else groupdict[group].append(name)}
如何存储我的理解代码以存储值列表,而不是仅存储最新值?除了使用setdefault()
函数或导入库之外,还有其他方法可以完成此操作吗?我应该在我的代码中仅包含for
,if
,else
和zip()
。
预先感谢您的帮助! :)
解决方法
使用dict.setdefault
例如:
students = ['Tom','Kitty','Jessie','Chester','Curie','Darwing','Nancy','Sue','Peter','Andrew','Karren','Charles','Nikhil','Justin','Astha']
assignment = [2,3,1,2,2]
result = {}
for k,v in zip(students,assignment):
result.setdefault(f"Group {v}",[]).append(k)
输出:
{'Group 1': ['Chester','Charles'],'Group 2': ['Tom','Astha'],'Group 3': ['Kitty','Nikhil']}
,
另一种解决方案,如果您想使用dict-comprehension(涉及使用itertools.groupby
和排序(Rakesh的答案在这方面更有效))
from itertools import groupby
students = ['Tom',2]
out = {'Group {}'.format(group): [s for s,_ in g] for group,g in groupby(sorted(zip(students,assignment),key=lambda k: k[1]),lambda k: k[1])}
print(out)
打印:
{'Group 1': ['Chester','Nikhil']}
,
使用defaultdict
var progressbar = document.querySelector ('.progressbar');
function ScrollProgressBar() {
var scrollTop = document.documentElement.scrollTop;
var scrollHeight = document.documentElement.scrollHeight;
var clientHeight = document.documentElement.clientHeight;
var windowHeight = scrollHeight - clientHeight;
var porcentaje = scrollTop / windowHeight * 100;
progressbar.style.height = porcentaje + '%';
}
window.addEventListener('scroll',ScrollProgressBar);
输出
from collections import defaultdict
result = defaultdict(list)
students = [
'Tom','Astha'
]
assignment = [2,2]
for k,assignment):
result[f"Group {v}"].append(k)
print(result)