Python: Convert string to code

Question

If I have the following dictionary:

foo = {'bar': {'baz': {'qux': 'gap'} } }

I want the user to be able to input "'bar','baz','qux','dop'" [expansion: " 'bar' , 'baz ' , 'qux' , 'dop' "] to convert:

{'qux': 'gap'}

to

{'qux': 'dop'}

I was hoping to approach this by converting the user input to a dictionary-lookup-statement (unsure of the exact term) through the following:

objectPath = "foo"
objectPathList = commandList[:-1]  # commandList is the user input converted to a list

for i in objectPathList:
    objectPath += "[" + i + "]"

changeTo = commandList[-1]

The above makes objectPath = "foo['bar']['baz']['qux']" and changeTo = 'dop'

Great! However, now I have been having issues with turning that statement into code. I thought eval() would do the trick, however the following seems not to work:

eval(objectPath) = changeTo

How can I convert the string objectPath to replace hard-written code?

eval(objectPath + "='" + changeTo "'")

L3viathan
– L3viathan

2016-03-20 23:50:17 +00:00
Commented Mar 20, 2016 at 23:50 — L3viathan
– L3viathan, Commented Mar 20, 2016 at 23:50
@L3viathan I can't believe I missed that! Thanks!

Jack
– Jack

2016-03-20 23:58:55 +00:00
Commented Mar 20, 2016 at 23:58 — Jack
– Jack, Commented Mar 20, 2016 at 23:58

molecule · Accepted Answer · 2016-03-21 00:10:09Z

1

I'd do something like this

foo = {'bar': {'baz': {'qux': 'gap'}}}
input = "'bar','baz','qux','dop'"

# Split the input into words and remove the quotes
words = [w.strip("'") for w in input.split(',')]

# Pop the last word (the new value) off of the list
new_val = words.pop()

# Get a reference to the inner dictionary ({'qux': 'gap'})
inner_dict = foo
for key in words[:-1]:
    inner_dict = inner_dict[key]

# assign the new value
inner_dict[words[-1]] = new_val

print("After:", foo)

answered Mar 21, 2016 at 0:10

molecule

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