The fourth bird questions

The fourth bird answers

• Extract content after colon if only one : exists in string
• How to capture two letters?
• PHP - Check for leading 0's in 2 comma-delimited integers
• How to ignore strings that start with certain pattern using regular expression in python?
• Find a substring that contains increased 1s
• How can I add a comma after each 3 digits?
• Delete string parts within delimiter
• Splitting a comma- and semicolon-delimited string in R
• Python 2.7 : matching expression using regex
• Invalid regular expression: look-behind requires fixed-width pattern