Python string contains check

To check if a string is part of another string (case sensitive) we can use these approaches

• Using in operator
• Using string find() method

  ## if start and end are present then search from start till end-1
  s.find(sub[, start[, end]])
  

• Using strng index() method. It is similar to find but raises ValueError. Its better to avoid it.

  ## if start and end are present then search from start till end-1
  s.index(sub[, start[, end]])
  

Case insensitive check

To do case insensitive check, both string can be converted to lowercase.

Example – contains check using in operator

s = "Hello Python"
sub = "Hello"
if sub in s:
  print "found"

found

Example – contains check using find(sub)

s = "Hello Python"
sub = "Hello"
if s.find(sub) >= 0:
  print "found at %s" % (s.find(sub))

found at 0

Example – contains check using index(sub)

Since this raises ValueError, it is better to use above approaches.

s = "Hello Python"
sub = "Hello2"
try:
  if s.index(sub) >= 0:
    print "found at %s" % (s.index(sub))
except ValueError as e:
  print str(e)

substring not found