Convert a string into a dictionary

Question

I have a string like "food | dairy | milk". The string may consist of more or less words. How do I turn it into a dictionary {'food': {'dairy': {'milk': {'eco': {}}}}}?

The only way I could achieve it was to create a string and then turn it into a dictionary using exec. I understand it's messy. How could I improve on it?

#!/usr/bin/env python -tt
# -*- coding: utf-8 -*-
# I have a string that represents 'path' to place where new item should be inserted
st="food | dairy | milk"
print st,"< -- string"
keys=st.split(" | ")
print keys,"<-- keys"
new_cat="eco" # should be added
d = {i:{} for i in keys}
print d,"d"
ex_str="{"
for i in keys:
 ex_str+="\""+i+"\":{"
ex_str+="\""+str(new_cat)+"\":{}"+"}"*(len(keys)+1)
exec"nd="+ex_str
print nd,"<-- new dict"

Answer 1

You use a temporary variable:

st="food | dairy | milk"
keys=st.split(" | ")
new_cat="eco" # should be added
d = t = {} # t is my temporary dictionary
for i in keys:
 t[i] = {}
 t = t[i]
t[new_cat] = {}
print d

Answer 2

Another way you can do it is going in reverse, like so:

st = "food | dairy | milk"
d = {}
new_cat="eco" # should be added
for key in reversed(st.split(" | ") + [new_cat]):
 d = {key: d}
print d
# {'food': {'dairy': {'milk': {'eco': {}}}}}

How this works is it starts with {}, then it does {the last key: what it is} ({'eco': {}}), then it does {the second to last key: what it is currently} ({'milk': {'eco': {}}}), and so on until the end.

But to make it more presentable, you should put it in a function. This also makes it more flexible, and allows it to work for more things.

def str_to_dict(separator, str_, *new_keys):
 d = {}
 for key in reversed(str_.split(seperator) + new_keys):
 d = {key: d}
 return d
print str_to_dict(" | ", "food | dairy | milk", "eco")
# {'food': {'dairy': {'milk': {'eco': {}}}}}
print str_to_dict("`", "food`dairy`milk", "eco", ("test",), 5)
# {'food': {'dairy': {'milk': {'eco': {('test',): {5: {}}}}}}}

• Sergii Artele: It looks interesting. Could you explain what does asterisk mean.
• user61114: @SergiiArtele The asterisk means that it can take as many arguments as it wants, and all the extra arguments will turn into a tuple called new_keys in this case. See stackoverflow.com/questions/36901/… as well.
• Sergii Artele: for key in reversed(str_.split(separator) + new_keys): TypeError: can only concatenate list (not "tuple") to list
• user61114: @SergiiArtele That seems to be a Python 2 issue. In that case, do reversed(str_.split(separator) + list(new_keys))
• Sergii Artele: THNX. Exactly, python 2.7