Here is how to check if a string contains a substring in Python.

# Define a string
my_string = "Hello, world!"

# Check if the string contains the substring "world"
if "world" in my_string:
    print("The string contains the substring.")
else:
    print("The string does not contain the substring.") 

Copy & Run

The string contains the substring.

---

Alternatively, you can use the find() method to check if a string contains a substring. This method returns the index of the first occurrence of the substring, or -1 if the substring is not found. Here's an example:

# Define a string
my_string = "Hello, world!"

# Find the index of the substring "world"
index = my_string.find("world")

# Check if the substring was found
if index != -1:
    print("The string contains the substring.")
else:
    print("The string does not contain the substring.")

This will also print 'The string contains the substring'.

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