CODEWITHSUNDEEP
pythonarrayslistdictionary
Ruchir
Ruchir

Reputation: 1122

How to search key from key-value pair in python

I have written code that is creating key-value pairs of a file from my computer and storing them in a list a. This is the code:

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

Now I want to find if a particular key is in that list or not. For example, my code generates this 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')]

Now,in output the keys are 'X', 'Y', 'Z', 'N' But the keys I'm looking for are A, B, G, F, M, N, S, X, Y, Z. So for those keys, that are not in output, the output should display something like "A not in list", "B not in list".

Upvotes: 3

Views: 5575

Answers (4)

Aneesh R P Prakkulam
Aneesh R P Prakkulam

Reputation: 219

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

Use List or Numpy array for mylist

Upvotes: 1

venpa
venpa

Reputation: 4318

You can read your tuples list as dict and check for key existence:

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"

Output:

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

Upvotes: 2

perreal
perreal

Reputation: 98078

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)

Gives:

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

Upvotes: 1

Amazingred
Amazingred

Reputation: 1007

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)

use a variable and a print function as you iterate through the list

I think this is what you want.

Upvotes: 3

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