How to check if string contains substring in Python

Using the in Operator

The easiest way to check if a Python string contains a substring is to use the in operator.

str = "Python"

if "th" in str:
  print("Found!")

# case-insensitive
if "TH" not in str:
  print("Not found!")

Found!
Not found!

Using str.Index Method

If the substring is not found, a ValueError exception is thrown, which can be handled with a try-except-else block:

str = "Python"

try:
  i = str.index("th")
  print(i)
  #Found!
except ValueError:
  print("Not found!")

Using str.find Method

Return the lowest index in the string where substring sub is found within the slice s[start:end]. Optional arguments start and end are interpreted as in slice notation. Return -1 if sub is not found.

str = "Python"

# str.find(sub[, start[, end]])
if str.find("th") != -1:
  print("Found!")

Found!