如何从 python 中的键值对中搜索键

Question

我编写了从我的计算机创建文件的键值对并将它们存储在列表a中的代码。 这是代码：

groups = defaultdict(list)
with open(r'/home/path....file.txt') as f:
    lines=f.readlines()
    lines=''.join(lines)
    lines=lines.split()
    a=[]
    for i in lines:
        match=re.match(r"([a,b,g,f,m,n,s,x,y,z]+)([-+]?[0-9]*\.?[0-9]+)",i,re.I)
        if match:
            a.append(match.groups())
print a

现在我想查找特定键是否在该列表中。 例如，我的代码生成这个 output：

[('X', '-6.511'),('Y', '-40.862'), 
('X', '-89.926'),('N', '7304'),
('X', '-6.272'), ('Y', '-40.868'), 
('X', '-89.979'),('N', '7305'),
('Y', '-42.101'),('Z', '238.517'),
('N', '7306'),   ('Y','-43.334'), 
('Z', '243.363'),('N', '7307')]

现在，在 output 中，键是'X' ， 'Y' ， 'Z' ， 'N'但我要找的键是A ， B ， G ， F ， M ， N ， S ， X ， Y ， Z . 因此，对于那些不在 output 中的键，output 应该显示类似"A not in list" ， "B not in list"内容。

Answer 1

for node in ['A', 'B', 'G', 'F', 'M', 'N', 'S', 'X', 'Y', 'Z']:
    if node not in groups.keys():
        print "%s not in list"%(node)

在遍历列表时使用变量和打印功能

我想这就是你想要的。

Answer 2

您可以将您的元组列表读取为dict并检查密钥是否存在：

d=[('X', '-6.511'),('Y', '-40.862'), 
('X', '-89.926'),('N', '7304'),
('X', '-6.272'), ('Y', '-40.868'), 
('X', '-89.979'),('N', '7305'),
('Y', '-42.101'),('Z', '238.517'),
('N', '7306'),   ('Y','-43.334'), 
('Z', '243.363'),('N', '7307')]

k=['A', 'B', 'G', 'F', 'M', 'N', 'S', 'X', 'Y', 'Z']
dt=dict(d)
for i in k:
    if i in dt:
        print i," has found"
    else:
        print i," has not found"

输出：

A  has not found
B  has not found
G  has not found
F  has not found
M  has not found
N  has found
S  has not found
X  has found
Y  has found
Z  has found

Answer 3

mylist = [('X', '-6.511'),('Y', '-40.862'), 
('X', '-89.926'),('N', '7304'),
('X', '-6.272'), ('Y', '-40.868'), 
('X', '-89.979'),('N', '7305'),
('Y', '-42.101'),('Z', '238.517'),
('N', '7306'),   ('Y','-43.334'), 
('Z', '243.363'),('N', '7307')]

missing = [ x for x in 'ABGFMNSXYZ' if x not in set(v[0] for v in mylist) ]
for m in missing:
    print "{} not in list".format(m)

得到：

A not in list
B not in list
G not in list
F not in list
M not in list
S not in list

Answer 4

if ('X', '-6.511') in mylist:
   print('Yes')
else:
   print('No')

对 mylist 使用 List 或 Numpy 数组