检查列表中是否存在值

Question

Let's say I have 123-0-1 and I want to check if this value exists inside the list. Below is the list that I have:

 df = [
       {'mpls': '123-0-1', 'source': '192.168.10.10', 'destination' : '12.168.100.10'}, 
       {'mpls': '123-0-1', 'source': '192.168.10.15', 'destination': '10.12.129.200'}
      ]

In SQL I would use:

select mpls, source from df where source = 192.168.10.10

From the list, I would like extract mpls 123-0-1 from the source 192.168.10.10 such that I can get the correct destination 12.168.100.10 .

Answer 1

df is not a dataframe. It is a list of dictionaries.

As such, your only option is a loop and an if condition:

for connection in df:
    if connection['source'] == '192.168.10.10':
        print(connection['mpls'])
        print(connection['destination'])
        # do whatever with connection. Can also break if it is guaranteed to be unique.

However, if df is a dataframe, you can use pandas indexing syntax:

relevant_rows = df[df['source'] == '192.168.10.10']

relevant_rows will then be a new dataframe whose rows are those where source equals '192.168.10.10' .

import pandas as pd

data = [
       {'mpls': '123-0-1', 'source': '192.168.10.10', 'destination' : '12.168.100.10'},
       {'mpls': '123-0-1', 'source': '192.168.10.15', 'destination': '10.12.129.200'}
      ]

df = pd.DataFrame(data)

print(df)

#         destination     mpls         source
#     0  12.168.100.10  123-0-1  192.168.10.10
#     1  10.12.129.200  123-0-1  192.168.10.15

relevant_rows = df[df['source'] == '192.168.10.10']

print(relevant_rows)

#         destination     mpls         source
#    0  12.168.100.10  123-0-1  192.168.10.10

Answer 2

Why not make a dataframe of it?

df = pd.DataFrame(df)
df[df['source'] == '192.168.10.10']

Answer 3

Here is a possible solution using list comprehension, as you are working with lists:

[(x['mpls'], x['destination']) for x in df if x['source'] == '192.168.10.10']

It returns a tuple with mpls and destination based on source :

[('123-0-1', '12.168.100.10')]

Answer 4

The other answers are just fine; just wanted to show how next could also be used:

df = [{'mpls': '123-0-1', 'source': '192.168.10.10', 'destination' : '12.168.100.10'}, {'mpls': '123-0-1', 'source': '192.168.10.15', 'destination': '10.12.129.200'}]

try:
  target = next(x for x in df if x['source'] == '192.168.10.10')
except StopIteration:
  print('Value not found!')
else:
  print(target['mpls'])         # -> 123-0-1
  print(target['destination'])  # -> 12.168.100.10

---

Note that this returns only the first dictionary that meets the criteria. based on your SQL statement, it seems that you want to get them all .

Answer 5

We can also use filter function to get filtered data from the list. filtered_list = filter((lambda x: x['source'] == '192.168.10.10'), df)