How can I assign a string value as an empty dictionary in Python? For example,
print hdr
AB_1_15_Oct_2015
hdr = {}
hdr
{}
But I want AB_1_15_Oct_2015 to be an empty dictionary.
3 Answers
Took a while to figure out, but try this:
hdr = "AB_1_15_Oct_2015"
print hdr
locals()[hdr] = {}
print AB_1_15_Oct_2015
Output:
AB_1_15_Oct_2015
{}
Comments
It's often considered a bad practice to dynamically assign variables like that. There are ways to do so, for instance using exec, but it is dangerous. A better idea would be to use a dictionary, since dynamically creating keys and values is simple. Slightly modifying your existing code:
hdr = "AB_1_15_Oct_2015"
someDict = {}
someDict[hdr] = {}
Then you could access it either from the top level
someDict[hdr]['a'] = "spam"
Or by assigning another variable to reference it:
hdrDict = someDict[hdr]
hdrDict['b'] = "parrot"
2 Comments
Saravana Thoppay
This solution too works for me. Thanks. I was struggling with the other way. Why do you call it dangerous?
Tofystedeth
The 'exec' and 'eval' statements allow Python to run strings as code. If these strings are coming from a user (as either text input, from a file, scanning file names a user may have access to, etc...) then it gives users a means to inject arbitrary code into your program. This is a huge security flaw. A less worse case scenario is that you are the one generating all the strings, and even then, an error can cause serious side effects, or problems that are difficult to debug.
If you are saying you want a dictionary named "AB_1_15_Oct_2015". You need to explicitly define a dictionary named:
AB_1_15_Oct_2015 = {}
If you mean you want to be able to set a variable name based off of a value in a string, then there is no way to accomplish this. Also, I can't think of a reason that you would want to. Variable names are only used internally in the code and therefore being able to change variable names based on the date wouldn't help you track a specific date. Without more information on what you are trying to accomplish, it's hard to be able to tell what you need, but I think something like this would accomplish what you want:
hdr = {
"identifier": "AB_1_15_Oct_2015",
"data": whatever_you_wanted_to_store
}
that way that identifier is attached to the data in an accessible way.
AB_1_15_Oct_2015 = {}??