Check if multiple strings exist in another string

Question

How can I check if any of the strings in an array exists in another string   Like   a     a    b    c   str    a123  if a in str    print  some of the strings found in str  else    print  no strings found in str    That code doesn t work  it s just to show what I want to achieve

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A compact way to find multiple strings in another list of strings is to use set intersection  This executes much faster than list comprehension in large sets or lists   gt  gt  gt  astring     abc   def   ghi   jkl   mno    gt  gt  gt  bstring     def    jkl    gt  gt  gt  a set   set astring     convert list to set  gt  gt  gt  b set   set bstring   gt  gt  gt  matches   a set intersection b set   gt  gt  gt  matches   def    jkl    gt  gt  gt  list matches    if you want a list instead of a set   def    jkl    gt  gt  gt

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flog   open  test txt    r   flogLines   flog readlines   strlist     SUCCESS    Done   SUCCESSFUL   res   False for line in flogLines       for fstr in strlist           if line find fstr     -1              print  found                res   True   if res      print  res true   else       print  res false

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You need to iterate on the elements of a   a     a    b    c   str    a123  found a string   False for item in a          if item in str          found a string   True  if found a string      print  found a match  else      print  no match found

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data    firstName and favoriteFood  mandatory fields     firstName    lastName    age       for each for field in mandatory fields      if field not in data          print  Error  missing req field  0   format field       still fine  multiple if statements if   firstName  not in data or       lastName  not in data or      age  not in data       print  Error  missing a req field       not very readable  list comprehension missing fields    x for x in mandatory fields if x not in data  if  len missing fields  gt 0       print  Error  missing fields  0   format      join missing fields

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Yet another solution with set  using set intersection  For a one-liner  subset     quot some quot    quot words quot    text    quot some words to be searched here quot  if len subset  amp  set text split        len subset      print  quot All values present in text quot    if subset  amp  set text split        print  quot Atleast one values present in text quot

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You can use any   a string    A string is more than its parts   matches     more    wholesome    milk    if any x in a string for x in matches     Similarly to check if all the strings from the list are found  use all instead of any

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You should be careful if the strings in a or str gets longer  The straightforward solutions take O S  A 2    where S is the length of str and A is the sum of the lenghts of all strings in a  For a faster solution  look at Aho-Corasick algorithm for string matching  which runs in linear time O S A

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jbernadas already mentioned the Aho-Corasick-Algorithm in order to reduce complexity   Here is one way to use it in Python    Download aho corasick py from here Put it in the same directory as your main Python file and name it aho corasick py Try the alrorithm with the following code   from aho corasick import aho corasick   string  keywords   print aho corasick string    keyword1    keyword2        Note that the search is case-sensitive

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I would use this kind of function for speed   def check string string  substring list       for substring in substring list          if substring in string              return True     return False

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Just to add some diversity with regex   import re  if any re findall r a b c   str  re IGNORECASE        print  possible matches thanks to regex  else      print  no matches    or if your list is too long - any re findall r    join a   str  re IGNORECASE

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A surprisingly fast approach is to use set   a     a    b    c   str    a123  if set a   amp  set str       print  some of the strings found in str   else      print  no strings found in str     This works if a does not contain any multiple-character values  in which case use any as listed above   If so  it s simpler to specify a as a string  a    abc

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a     a    b    c   str     a123   a match    True for match in a if match in str   if True in a match    print  some of the strings found in str  else    print  no strings found in str

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It depends on the  context  suppose if you want to check single literal like any single word a e w   etc  in is enough  original word   hackerearcth  for  h  in original word        print  YES     if you want to check any of the character among the original word  make use of   if any your required in yourinput for your required in original word      if you want all the input you want in that  original word make use of all simple  original word     h    a    c    k    e    r    e    a    r    t    h   yourinput   str input    lower   if all requested word in yourinput for requested word in original word       print  yes

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any   is by far the best approach if all you want is True or False  but if you want to know specifically which string strings match  you can use a couple things   If you want the first match  with False as a default    match   next  x for x in a if x in str   False    If you want to get all matches  including duplicates    matches    x for x in a if x in str    If you want to get all non-duplicate matches  disregarding order    matches    x for x in a if x in str    If you want to get all non-duplicate matches in the right order   matches      for x in a      if x in str and x not in matches          matches append x

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The regex module recommended in python docs  supports this words     he    or    low   p   regex compile r quot  L lt name gt  quot   name words  m   p findall  helloworld   print m   output    he    low    or    Some details on implementation  link

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Just some more info on how to get all list elements availlable in String  a     a    b    c   str    a123   list filter lambda x   x in str  a

[python] Check if multiple strings exist in another string

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