Tag: Dictionary

Converting two-column DataFrame to a dictionary in Python

If you have a Pandas dataframe like the following (if you already have a DataFrame based on a query result, you can use that):

import pandas as pd
data = [['tom', 10], ['nick', 15], ['juli', 14]]
df = pd.DataFrame(data, columns = ['Name', 'Age'])
Basic Pandas DataFrame

I wanted a dictionary where I could provide the name (“tom”, “nick”, or “juli”) and receive their age as the result. To convert your DataFrame to a dictionary like this, you’d use the following command:

my_dict = pd.Series(df.Age.values,index=df.Name).to_dict()
print(my_dict)
Python dict with three key:value pairs

Now that you have a dictionary, you can do lookups or whatever else you want. Make sure you take note above that the first parameter uses “values” where the second one doesn’t. If you use values in the second parameter, or you just try to use the “.todict()” function on the DataFrame directly, without converting it to a series first as above, you can end up with Dictionaries with an entry for each column, or dictionaries that contain dictionaries, or a number of other things that don’t work.

Short and to the point – this took me about an hour to find the answer to and hopefully you find it before losing that much time!

Periodic timeouts with local WCF endpoint

I have two applications – a Windows service and a client WinForm – that run on the same box, and the client needs to check on the status of the service every few seconds. It worked well most of the time, but every 4-5 times, it would timeout – I’d receive a System.TimeoutException, no matter how long the timeout was actually set for. It didn’t make sense – the two apps are on the same box, it happens with both a TCP and an NamedPipe endpoint, and it can happen even when the service isn’t busy.

It turns out that WCF endpoints only handle a very limited number of simultanious connections, and though I was creating a new ChannelFactory each time, I wasn’t closing the channel when I was finished with it. I assumed that it would automatically close the channel when it passed out of scope, but no dice. Since the channels remained open, it didn’t take long to fill them all up, and then the app would appear to be unresponsive until my channels started to time out. So here’s what I ended up doing – critical line in bold, at the end:

Dim tcpBinding As New NetTcpBinding
Dim pipeFactory As ChannelFactory(Of WCF_Class.IServiceRemoting) = New  _
    ChannelFactory(Of WCF_Class.IServiceRemoting)(tcpBinding, "net.tcp://localhost:4079")
Dim ServiceWCFConnection As WCF_Class.IServiceRemoting = pipeFactory.CreateChannel
MessageBox.Show(ServiceWCFConnection.Responsive)
pipeFactory.Close() ' This is what's important!

That’s it – make sure you close your Channel when you’re done with it! If you leave it open, you quickly hit the server’s connection limit and new requests will fail. Closing the channel when you’re done frees it up, instead of letting it time out and close on its own.