I continue to work on an assignment and I have another problem that has taken much time to overcome without success. The question is as follows:

$22.$ Implement the Function get$\_$src

Implement the function according to the specification. An ideal solution will use first$\_$inside$\_$quotes as a helper. Use the test script testcurrency.py to aid your development before checking your answer below.

My answer is:

pos$1=$ introcs.find$\_$str$($json$,\text{'}"\text{'})$

pos$2=$ introcs.find$\_$str$($json$,\text{'}",\text{'},$ pos$1+25)$

return json$[$pos$1+25$:pos$2]$

I get the following error message:

Call get$\_$src$(\text{'}\{"$success$"$: false, $"$src$"$: $"","$dst$"$: $"",$ "error": "The rate for currency EUF is not present."$\}\text{'})$ returned $\text{'}"\text{'},$ not the expected $\text{'}\text{'}.$

Another answer based on an answer from your experts on a previous occasion is:

def get$\_$src$($json$)$:

$"""$

Returns the src value in the response to a currency query.

Given a JSON string provided by the web service, this function returns

the string inside string quotes $(")$ immediately following the substring $\text{'}"$src$"\text{'}.$

For example, if the json is $\text{'}\{"$success$"$: true, $"$src$"$: $"2$ United States Dollars",

$"$dst$"$: $"1\mathrm{.}772814$ Euros", "error": $""\}\text{'},$ then this function returns

$\text{'}2$ United States Dollars' $($not $\text{'}"2$ United States Dollars"$\text{'}).$

On the other hand, if the json is $\text{'}\{"$success$"$: false, $"$src$"$:$"","$dst$"$:$"",$

"error":"Source currency code is invalid."$\}\text{'},$ then this function returns

the empty string.

Parameter json: a json string to parse

Precondition: json is a string provided by the web service $($ONLY enforce the type$)$

$"""$

start $=$ json.find$(\text{'}"$src$"\text{'})+$ len$(\text{'}"$src$"\text{'})+1$ # Find the starting index of the value

end $=$ json.find$(\text{'}"\text{'},$ start$)$ # Find the ending index of the value

return json$[$start:end$]$ # Extract and return the value between the quotes

I get the following error message:

Call get$\_$src$(\text{'}\{"$success$"$: true, $"$src$"$: $"2\mathrm{.}5$ United States Dollars", $"$dst$"$: $"2\mathrm{.}28242$ Euros", "error": $""\}\text{'})$ returned $\text{'}\text{'},$ not the expected $\text{'}2\mathrm{.}5$ United States Dollars'.

I also tried the following:

start $=$ json.find$(\text{'}"$src$"\text{'})+$ len$(\text{'}"$src$"\text{'})+3$ # Find the starting index of the value

end $=$ json.find$(\text{'}"\text{'},$ start$)$ # Find the ending index of the value

return json$[$start:end$]$ # Extract and return the value between the quotes

I still get the error following message:

Call get$\_$src$(\text{'}\{"$success$"$:true, $"$src$"$:$"2\mathrm{.}5$ United States Dollars", $"$dst$"$:$"2\mathrm{.}28242$ Euros", "error":""$\}\text{'})$ returned $\text{'}\mathrm{.}5$ United States Dollars', not the expected $\text{'}2\mathrm{.}5$ United States Dollars'.

It is interesting that even your answer$-$ from a previous occasion $-$ still gives an error message. I would appreciate your help as I have wasted sufficient time on this. Thank you...