Python match a string with regex

Question

I need a python regular expression to check if a word is present in a string  The string is separated by commas  potentially   So for example   line    This is a sample string    I want to search based on  sample   this would return true  I am crappy with reg ex  so when I looked at the python docs  I saw something like  import re re match r sample   line    But I don t know why there was an  r  before the text to be matched  Can someone help me with the regular expression

User · Answer

r stands for a raw string  so things like   will be automatically escaped by Python   Normally  if you wanted your pattern to include something like a backslash you d need to escape it with another backslash  raw strings eliminate this problem   short explanation  In your case  it does not matter much but it s a good habit to get into early otherwise something like  b will bite you in the behind if you are not careful  will be interpreted as backspace character instead of word boundary    As per re match vs re search here s an example that will clarify it for you    gt  gt  gt  import re  gt  gt  gt  testString    hello world   gt  gt  gt  re match  hello   testString   lt  sre SRE Match object at 0x015920C8 gt   gt  gt  gt  re search  hello   testString   lt  sre SRE Match object at 0x02405560 gt   gt  gt  gt  re match  world   testString   gt  gt  gt  re search  world   testString   lt  sre SRE Match object at 0x015920C8 gt    So search will find a match anywhere  match will only start at the beginning

User · Answer

As everyone else has mentioned it is better to use the  in  operator  it can also act on lists   line    This is a sample string  lst     This    sample   for i in lst       i in line   gt  gt  True  gt  gt  True

User · Answer

Are you sure you need a regex  It seems that you only need to know if a word is present in a string  so you can do    gt  gt  gt  line    This is a sample string   gt  gt  gt   sample  in line  True

User · Answer

The r makes the string a raw string  which doesn t process escape characters  however  since there are none in the string  it is actually not needed here    Also  re match matches from the beginning of the string   In other words  it looks for an exact match between the string and the pattern   To match stuff that could be anywhere in the string  use re search   See a demonstration below    gt  gt  gt  import re  gt  gt  gt  line    This is a sample string   gt  gt  gt  re match  sample   line   gt  gt  gt  re search  sample   line   lt  sre SRE Match object at 0x021D32C0 gt   gt  gt  gt

User · Answer

One Liner implementation   a  1 3  b  1 2 3 4  all i in b for i in a

User · Answer

You do not need regular expressions to check if a substring exists in a string   line    This is a sample string  result   bool  sample  in line    returns True   If you want to know if a string contains a pattern then you should use re search  line    This is a sample string  result   re search r sample   line    finds  sample    This is best used with pattern matching  for example   line    my name is bob  result   re search r my name is   S     line    finds  bob

[python] Python match a string with regex

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