Parse long string to retrieve channel

I have extracted a lot of data from Telegram. However, I was not able to isolate the channel_id. Now I have a long string that among a lot of other information contain channel_id. Question is how do I remove everything apart from the channel_id i.e. the numbers following "channel_id=XXXXXXXXXX)?

Subset of my data.frame

df <- structure(list(channel_id = c("MessageFwdHeader(date=datetime.datetime(2021, 5, 13, 20, 50, 47, tzinfo=datetime.timezone.utc), imported=False, from_id=PeerChannel(channel_id=1292436059), from_name=None, channel_post=1404, post_author=None, saved_from_peer=None, saved_from_msg_id=None, psa_type=None)", 
                                      "MessageFwdHeader(date=datetime.datetime(2021, 5, 4, 9, 24, 16, tzinfo=datetime.timezone.utc), imported=False, from_id=PeerChannel(channel_id=1480423705), from_name=None, channel_post=224, post_author=None, saved_from_peer=None, saved_from_msg_id=None, psa_type=None)", 
                                      "MessageFwdHeader(date=datetime.datetime(2021, 3, 25, 14, 9, 38, tzinfo=datetime.timezone.utc), imported=False, from_id=PeerChannel(channel_id=1489900933), from_name=None, channel_post=627, post_author=None, saved_from_peer=None, saved_from_msg_id=None, psa_type=None)", 
                                      "MessageFwdHeader(date=datetime.datetime(2021, 3, 12, 22, 10, 3, tzinfo=datetime.timezone.utc), imported=False, from_id=PeerChannel(channel_id=1455689590), from_name=None, channel_post=1457, post_author=None, saved_from_peer=None, saved_from_msg_id=None, psa_type=None)", 
                                      "MessageFwdHeader(date=datetime.datetime(2021, 3, 9, 12, 52, 5, tzinfo=datetime.timezone.utc), imported=False, from_id=PeerChannel(channel_id=1348575245), from_name=None, channel_post=None, post_author=None, saved_from_peer=None, saved_from_msg_id=None, psa_type=None)"
)), row.names = c(NA, -5L), class = c("data.table", "data.frame"))

Desired result

channel_id <- structure(list(channel_id = c("1292436059", 
                                            "1480423705", 
                                            "1489900933", 
                                            "1455689590", 
                                            "1348575245"
)), row.names = c(NA, -5L), class = c("data.table", "data.frame"))

CodePudding user response：

You can try regexpr with a look behind for (channel_id= using (?<=\\(channel_id=), than match digit(s) \\d and look ahead for ) using (?=\\)) and extract the matches using regmatches.

regmatches(df$channel_id, regexpr("(?<=\\(channel_id=)\\d (?=\\))"
          , df$channel_id, perl=TRUE))
#[1] "1292436059" "1480423705" "1489900933" "1455689590" "1348575245"

or combining two sub.

sub(").*", "", sub(".*\\(channel_id=", "", df$channel_id))
#[1] "1292436059" "1480423705" "1489900933" "1455689590" "1348575245