Str.extract(r'(\d+)')--- what does' \d+' mean?

Q&A
#1

Hi all! dont understand the pattern (r'(\d+)'), what we want to do here?

My Code: 

combined_updated['institute_service_updated']=combined_updated['institute_service'].astype(str).str.extract(r'(\d+)')

What I expected to happen:

What actually happened:

Replace this line with the output/error
1 Like
#2

Regex isn’t one of my strong points, but according to regexr it’s a character that matches one or more digits (0-9)

#3

This is a Regular Expression pattern \d is a regex pattern for digit + is a regex pattern for at least (one or more) since they are enclosed in a ( ) that means the group that you want to capture.

Regex Explanation:

Extract/capture one or more digit (0 - 9)

2 Likes
#4

Hi @info.victoromondi
Thank you for you answering!!
so r'\d+' means to capture 1 digit? In the instruction, we learned {}. it means that how many time we want the number or letter to repeat. Why dont we need to use here to indicate the pattern?

#5

\d is for one digit only eg 1
\d+ one or more (at least one digit) digit eg 1 or 34 or 983434 etc.

3 Likes
#6

You mentined that () enclosed r'\d+' mean that i want to capture the group. For example, the value is 04/2016. how can python know to capture 2016 instead of 04?

Thank you again!

#7

04 will be extracted. Consider this example

In [7]: df = pd.DataFrame({'dt':[str(num)+'/' + str(2000+num) for num in range(5)], 'name':list('victo')})

In [8]: df
Out[8]:
       dt name
0  0/2000    v
1  1/2001    i
2  2/2002    c
3  3/2003    t
4  4/2004    o

In [9]: df.dt.str.extract(r"(\d+)")
Out[9]:
   0
0  0
1  1
2  2
3  3
4  4
#8

Got you thank you!

if i want to extract year in your example, then how to do it? in the regular way only str.split('/').str[-1]?