Does Python have a string ‘contains’ substring method?

Yes. Python has an inbuilt string method contains() which helps find if a string contains a specific substring or not. 

Syntax: 

demostring.__contains__(substring)

The function takes in two strings, the original string and the substring whose presence is to be checked. It returns a boolean value, True if the substring is present in the string, else False. 

Example:

string_demo= "Python by i2tutorials"
sub_string_1="Python"
sub_string_2="Java"

result= string_demo.__contains__(sub_string_1)
result_2= string_demo.__contains__(sub_string_2)

print(result)
print(result_2)

Output:

We can use this string contains method as a class method too. The syntax for the same looks like this:

str.__contains__(demostring,substring)

Example:

string_demo= "Python by i2tutorials"
sub_string_1="Python"
sub_string_2="Java"

result= str.__contains__(string_demo,sub_string_1)
result_2= str.__contains__(string_demo,sub_string_2)

print(result)
print(result_2)

Output:

This method raises TypeError exception when the demo string points to None. 

Example:

string_demo= None
sub_string="Python"

result= str.__contains__(string_demo,sub_string)

print(result)

Output:

To avoid this, we have to check whether our demo string points to None or not. Here, we use an if-else statement to do this.

Example:

string_demo= None
sub_string="Python"

if string_demo != None:
   print(str.__contains__(string_demo,sub_string_1))
else:
   print("The demo string is empty")

Output: