Get text after string

I'm looking for help to create a regular expression that can get a certain text after a given string using Python.

I'm trying to extract a JSON from a page and it's like this:

    var config = {aslkdjsakljdkalsj{asdasdas}askldjaskljd};

I need a regex that can get from the first { to the } => without the semicolon

I've tried using

    config = .*?(?=};)

but the output is

    config = {sadasdasdas{a}asdasdasd

It gets the config = part and doesn't get the last }.

How can I fix it?

edited Jan 4 at 0:46

CertainPerformance

97.5k165887

asked Jan 3 at 1:42

Tauan Matos

133

What language are you implementing this in?

– CertainPerformance
Jan 3 at 1:43

Also, {aslkdjsakljdkalsj{asdasdas}askldjaskljd}; is not JSON

– CertainPerformance
Jan 3 at 1:44

I'm not implementing yet. I'm trying to find the right pattern using link.

– Tauan Matos
Jan 3 at 1:48

And yes, in this example it's not a JSON.

– Tauan Matos
Jan 3 at 1:48

Which language you're using really matters - in some languages, this is impossible, in others, it's doable.

– CertainPerformance
Jan 3 at 1:50

|
show 5 more comments

I'm looking for help to create a regular expression that can get a certain text after a given string using Python.

I'm trying to extract a JSON from a page and it's like this:

    var config = {aslkdjsakljdkalsj{asdasdas}askldjaskljd};

I need a regex that can get from the first { to the } => without the semicolon

I've tried using

    config = .*?(?=};)

but the output is

    config = {sadasdasdas{a}asdasdasd

It gets the config = part and doesn't get the last }.

How can I fix it?

edited Jan 4 at 0:46

CertainPerformance

97.5k165887

asked Jan 3 at 1:42

Tauan Matos

133

What language are you implementing this in?

– CertainPerformance
Jan 3 at 1:43

Also, {aslkdjsakljdkalsj{asdasdas}askldjaskljd}; is not JSON

– CertainPerformance
Jan 3 at 1:44

I'm not implementing yet. I'm trying to find the right pattern using link.

– Tauan Matos
Jan 3 at 1:48

And yes, in this example it's not a JSON.

– Tauan Matos
Jan 3 at 1:48

Which language you're using really matters - in some languages, this is impossible, in others, it's doable.

– CertainPerformance
Jan 3 at 1:50

|
show 5 more comments

I'm looking for help to create a regular expression that can get a certain text after a given string using Python.

I'm trying to extract a JSON from a page and it's like this:

    var config = {aslkdjsakljdkalsj{asdasdas}askldjaskljd};

I need a regex that can get from the first { to the } => without the semicolon

I've tried using

    config = .*?(?=};)

but the output is

    config = {sadasdasdas{a}asdasdasd

It gets the config = part and doesn't get the last }.

How can I fix it?

edited Jan 4 at 0:46

CertainPerformance

97.5k165887

asked Jan 3 at 1:42

Tauan Matos

133

I'm looking for help to create a regular expression that can get a certain text after a given string using Python.

I'm trying to extract a JSON from a page and it's like this:

    var config = {aslkdjsakljdkalsj{asdasdas}askldjaskljd};

I need a regex that can get from the first { to the } => without the semicolon

I've tried using

    config = .*?(?=};)

but the output is

    config = {sadasdasdas{a}asdasdasd

It gets the config = part and doesn't get the last }.

How can I fix it?

python regex

edited Jan 4 at 0:46

CertainPerformance

97.5k165887

asked Jan 3 at 1:42

Tauan Matos

133

edited Jan 4 at 0:46

CertainPerformance

97.5k165887

asked Jan 3 at 1:42

Tauan Matos

133

edited Jan 4 at 0:46

CertainPerformance

97.5k165887

edited Jan 4 at 0:46

CertainPerformance

97.5k165887

edited Jan 4 at 0:46

CertainPerformance

97.5k165887

asked Jan 3 at 1:42

Tauan Matos

133

asked Jan 3 at 1:42

Tauan Matos

133

asked Jan 3 at 1:42

Tauan Matos

133

What language are you implementing this in?

– CertainPerformance
Jan 3 at 1:43

Also, {aslkdjsakljdkalsj{asdasdas}askldjaskljd}; is not JSON

– CertainPerformance
Jan 3 at 1:44

I'm not implementing yet. I'm trying to find the right pattern using link.

– Tauan Matos
Jan 3 at 1:48

And yes, in this example it's not a JSON.

– Tauan Matos
Jan 3 at 1:48

Which language you're using really matters - in some languages, this is impossible, in others, it's doable.

– CertainPerformance
Jan 3 at 1:50

|
show 5 more comments

What language are you implementing this in?

– CertainPerformance
Jan 3 at 1:43

Also, {aslkdjsakljdkalsj{asdasdas}askldjaskljd}; is not JSON

– CertainPerformance
Jan 3 at 1:44

I'm not implementing yet. I'm trying to find the right pattern using link.

– Tauan Matos
Jan 3 at 1:48

And yes, in this example it's not a JSON.

– Tauan Matos
Jan 3 at 1:48

Which language you're using really matters - in some languages, this is impossible, in others, it's doable.

– CertainPerformance
Jan 3 at 1:50

What language are you implementing this in?

– CertainPerformance
Jan 3 at 1:43

Also, {aslkdjsakljdkalsj{asdasdas}askldjaskljd}; is not JSON

– CertainPerformance
Jan 3 at 1:44

I'm not implementing yet. I'm trying to find the right pattern using link.

– Tauan Matos
Jan 3 at 1:48

And yes, in this example it's not a JSON.

– Tauan Matos
Jan 3 at 1:48

Which language you're using really matters - in some languages, this is impossible, in others, it's doable.

– CertainPerformance
Jan 3 at 1:50

|
show 5 more comments

1 Answer
1

active

oldest

votes

If your line of JS there is guaranteed to contain no newline characters before the terminating ;, then the problem is simple enough - match var config =, followed by non-newline characters captured in a group, and then matcha semicolon and the end of the line. If the JSON is delimited with 's, then, for example, use the pattern

var config = '(.+)';$

and extract the first group.

input = '''

  var config = '{ "foo": "b\ar", "ba{{}}}{{z": ["buzz}", "qux", {"innerprop": "innerval"}]}';

  var someOtherVar = 'bar';

'''

match = re.search("(?m)var config = '(.+)';$", input);

If the JSON isn't guaranteed to be on its own line, then it's a lot more complicated. Parsing nested structures like JSON is difficult - the only way the general problem is solvable with regular expressions is if the structure is known beforehand (which often isn't the case, and can require a lot of repetitive code in the pattern), or if the RE engine being used supports recursive matches. Without that, there's no way to to express the need for a balanced number of {s with }s in the pattern.

Luckily, if you're working with Python, even though Python's native REs don't support recursion, there'a a regex module available that does. You'll also need to make sure that the { and }s that may come inside of strings in the JSON don't affect the current nesting level. For a raw string, you'd need a pattern like

var config = String.raw`K({(?:"(?:\|\"|[^"])*"|[^{}]|(?1))*})(?=`;)

The outside of the capture group is

var config = String.raw`K({ ... })(?=`;)

matching the line you want and the string delimiters, with a capturing group of

{(?:"(?:\|\"|[^"])*"|[^{}]|(?1))*}

which means - {, followed by any number of: either

"(?:\|\"|[^"])*" - match a string inside the JSON (either a key or a value), from its starting delimiter to its ending delimiter, ignoring escaped "s, or

[^{}] - Match anything that isn't a { or } - other characters can be ignored, since we just want to get the nesting level right, or

(?1) - Recurse the whole first capture group (the one that matches the { ... })

This will ensure that the { } brackets are balanced by the end of the pattern.

But - the above is an example where String.raw was used, where literal backslashes in the Javascript code indicate literal backslashes in the string. With ' delimiters, on the other hand, literal backslashes need to be double-escaped in the JS, so the above input would look like

var config = '{ "foo": "b\\ar", "ba{{}}}{{z": ["buzz}", "qux", {"innerprop": "innerval"}]}';

requiring double-escaping the backslashes in the pattern as well:

var config = 'K({(?:"(?:\\|\\"|[^"])*"|[^{}]|(?1))*})(?=';)

https://regex101.com/r/8rSrGf/1

It's pretty complicated. I'd recommend going with the first approach or a variation on it instead, if at all possible.

answered Jan 4 at 0:44

CertainPerformance

97.5k165887

Thanks for the editing and answer. Really helped me.

– Tauan Matos
Jan 6 at 3:37

add a comment |

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1 Answer
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var config = '(.+)';$

and extract the first group.

input = '''

  var config = '{ "foo": "b\ar", "ba{{}}}{{z": ["buzz}", "qux", {"innerprop": "innerval"}]}';

  var someOtherVar = 'bar';

'''

match = re.search("(?m)var config = '(.+)';$", input);

var config = String.raw`K({(?:"(?:\|\"|[^"])*"|[^{}]|(?1))*})(?=`;)

The outside of the capture group is

var config = String.raw`K({ ... })(?=`;)

matching the line you want and the string delimiters, with a capturing group of

{(?:"(?:\|\"|[^"])*"|[^{}]|(?1))*}

which means - {, followed by any number of: either

"(?:\|\"|[^"])*" - match a string inside the JSON (either a key or a value), from its starting delimiter to its ending delimiter, ignoring escaped "s, or

[^{}] - Match anything that isn't a { or } - other characters can be ignored, since we just want to get the nesting level right, or

(?1) - Recurse the whole first capture group (the one that matches the { ... })

This will ensure that the { } brackets are balanced by the end of the pattern.

var config = '{ "foo": "b\\ar", "ba{{}}}{{z": ["buzz}", "qux", {"innerprop": "innerval"}]}';

requiring double-escaping the backslashes in the pattern as well:

var config = 'K({(?:"(?:\\|\\"|[^"])*"|[^{}]|(?1))*})(?=';)

https://regex101.com/r/8rSrGf/1

It's pretty complicated. I'd recommend going with the first approach or a variation on it instead, if at all possible.

answered Jan 4 at 0:44

CertainPerformance

97.5k165887

Thanks for the editing and answer. Really helped me.

– Tauan Matos
Jan 6 at 3:37

add a comment |

var config = '(.+)';$

and extract the first group.

input = '''

  var config = '{ "foo": "b\ar", "ba{{}}}{{z": ["buzz}", "qux", {"innerprop": "innerval"}]}';

  var someOtherVar = 'bar';

'''

match = re.search("(?m)var config = '(.+)';$", input);

var config = String.raw`K({(?:"(?:\|\"|[^"])*"|[^{}]|(?1))*})(?=`;)

The outside of the capture group is

var config = String.raw`K({ ... })(?=`;)

matching the line you want and the string delimiters, with a capturing group of

{(?:"(?:\|\"|[^"])*"|[^{}]|(?1))*}

which means - {, followed by any number of: either

"(?:\|\"|[^"])*" - match a string inside the JSON (either a key or a value), from its starting delimiter to its ending delimiter, ignoring escaped "s, or

[^{}] - Match anything that isn't a { or } - other characters can be ignored, since we just want to get the nesting level right, or

(?1) - Recurse the whole first capture group (the one that matches the { ... })

This will ensure that the { } brackets are balanced by the end of the pattern.

var config = '{ "foo": "b\\ar", "ba{{}}}{{z": ["buzz}", "qux", {"innerprop": "innerval"}]}';

requiring double-escaping the backslashes in the pattern as well:

var config = 'K({(?:"(?:\\|\\"|[^"])*"|[^{}]|(?1))*})(?=';)

https://regex101.com/r/8rSrGf/1

It's pretty complicated. I'd recommend going with the first approach or a variation on it instead, if at all possible.

answered Jan 4 at 0:44

CertainPerformance

97.5k165887

Thanks for the editing and answer. Really helped me.

– Tauan Matos
Jan 6 at 3:37

add a comment |

var config = '(.+)';$

and extract the first group.

input = '''

  var config = '{ "foo": "b\ar", "ba{{}}}{{z": ["buzz}", "qux", {"innerprop": "innerval"}]}';

  var someOtherVar = 'bar';

'''

match = re.search("(?m)var config = '(.+)';$", input);

var config = String.raw`K({(?:"(?:\|\"|[^"])*"|[^{}]|(?1))*})(?=`;)

The outside of the capture group is

var config = String.raw`K({ ... })(?=`;)

matching the line you want and the string delimiters, with a capturing group of

{(?:"(?:\|\"|[^"])*"|[^{}]|(?1))*}

which means - {, followed by any number of: either

"(?:\|\"|[^"])*" - match a string inside the JSON (either a key or a value), from its starting delimiter to its ending delimiter, ignoring escaped "s, or

[^{}] - Match anything that isn't a { or } - other characters can be ignored, since we just want to get the nesting level right, or

(?1) - Recurse the whole first capture group (the one that matches the { ... })

This will ensure that the { } brackets are balanced by the end of the pattern.

var config = '{ "foo": "b\\ar", "ba{{}}}{{z": ["buzz}", "qux", {"innerprop": "innerval"}]}';

requiring double-escaping the backslashes in the pattern as well:

var config = 'K({(?:"(?:\\|\\"|[^"])*"|[^{}]|(?1))*})(?=';)

https://regex101.com/r/8rSrGf/1

It's pretty complicated. I'd recommend going with the first approach or a variation on it instead, if at all possible.

answered Jan 4 at 0:44

CertainPerformance

97.5k165887

var config = '(.+)';$

and extract the first group.

input = '''

  var config = '{ "foo": "b\ar", "ba{{}}}{{z": ["buzz}", "qux", {"innerprop": "innerval"}]}';

  var someOtherVar = 'bar';

'''

match = re.search("(?m)var config = '(.+)';$", input);

var config = String.raw`K({(?:"(?:\|\"|[^"])*"|[^{}]|(?1))*})(?=`;)

The outside of the capture group is

var config = String.raw`K({ ... })(?=`;)

matching the line you want and the string delimiters, with a capturing group of

{(?:"(?:\|\"|[^"])*"|[^{}]|(?1))*}

which means - {, followed by any number of: either

"(?:\|\"|[^"])*" - match a string inside the JSON (either a key or a value), from its starting delimiter to its ending delimiter, ignoring escaped "s, or

[^{}] - Match anything that isn't a { or } - other characters can be ignored, since we just want to get the nesting level right, or

(?1) - Recurse the whole first capture group (the one that matches the { ... })

This will ensure that the { } brackets are balanced by the end of the pattern.

var config = '{ "foo": "b\\ar", "ba{{}}}{{z": ["buzz}", "qux", {"innerprop": "innerval"}]}';

requiring double-escaping the backslashes in the pattern as well:

var config = 'K({(?:"(?:\\|\\"|[^"])*"|[^{}]|(?1))*})(?=';)

https://regex101.com/r/8rSrGf/1

It's pretty complicated. I'd recommend going with the first approach or a variation on it instead, if at all possible.

answered Jan 4 at 0:44

CertainPerformance

97.5k165887

answered Jan 4 at 0:44

CertainPerformance

97.5k165887

answered Jan 4 at 0:44

CertainPerformance

97.5k165887

answered Jan 4 at 0:44

CertainPerformance

97.5k165887

Thanks for the editing and answer. Really helped me.

– Tauan Matos
Jan 6 at 3:37

add a comment |

Thanks for the editing and answer. Really helped me.

– Tauan Matos
Jan 6 at 3:37

Thanks for the editing and answer. Really helped me.

– Tauan Matos
Jan 6 at 3:37

add a comment |

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