How can I check if a string contains ANY letters from the alphabet

Question

What is best pure Python implementation to check if a string contains ANY letters from the alphabet   string 1     555  555-5555  string 2     555  555 - 5555 ext  5555   Where string 1 would return False for having no letters of the alphabet in it and string 2 would return True for having letter

User · Answer

I liked the answer provided by  jean-fran  ois-fabre  but it is incomplete  His approach will work  but only if the text contains purely lower- or uppercase letters    gt  gt  gt  text     555  555-5555 extA  5555   gt  gt  gt  text islower   False  gt  gt  gt  text isupper   False   The better approach is to first upper- or lowercase your string and then check    gt  gt  gt  string1     555  555-5555 extA  5555   gt  gt  gt  string2    555  234  - 123 32   21    gt  gt  gt  string1 upper   isupper   True  gt  gt  gt  string2 upper   isupper   False

User · Answer

How about    gt  gt  gt  string 1     555  555-5555   gt  gt  gt  string 2     555  555 - 5555 ext  5555   gt  gt  gt  any c isalpha   for c in string 1  False  gt  gt  gt  any c isalpha   for c in string 2  True

User · Answer

You can use islower   on your string to see if it contains some lowercase letters  amongst other characters   or it with isupper   to also check if contains some uppercase letters   below  letters in the string  test yields true   gt  gt  gt  z     555  555 - 5555 ext  5555   gt  gt  gt  z isupper   or z islower   True   below  no letters in the string  test yields false    gt  gt  gt  z    555  555-5555   gt  gt  gt  z isupper   or z islower   False  gt  gt  gt     Not to be mixed up with isalpha   which returns True only if all characters are letters  which isn t what you want   Note that Barm s answer completes mine nicely  since mine doesn t handle the mixed case well

User · Answer

You can use regular expression like this   import re  print re search   a-zA-Z    string

User · Answer

You can also do this in addition  import re string  24234ww  val   re search   a-zA-Z    string   val 0  isalpha     returns True if the variable is an alphabet print val 0     this will print the first instance of the matching value   Also note that if variable val returns None  That means the search did not find a match

User · Answer

I tested each of the above methods for finding if any alphabets are contained in a given string and found out average processing time per string on a standard computer    250 ns for  import re    3   s for  re search   a-zA-Z    string     6   s for  any c isalpha   for c in string     850 ns for  string upper   isupper     Opposite to as alleged  importing re takes negligible time  and searching with re takes just about half time as compared to iterating isalpha   even for a relatively small string  Hence for larger strings and greater counts  re would be significantly more efficient   But converting string to a case and checking case  i e  any of upper   isupper   or lower   islower     wins here  In every loop it is significantly faster than re search   and it doesn t even require any additional imports

User · Answer

Regex should be a fast approach   re search   a-zA-Z    the string

[python] How can I check if a string contains ANY letters from the alphabet?

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