Startswith, `endswith`

All Python strings have a start and an end. Often we need to test the starts and ends of strings. We use the startswith and endswith methods.

We can take a substring and compare that to a string—this can do the same thing as startswith or endswith. But with specialized methods, our code is clearer and likely faster.

Example

Here we have a string that has many characters in it. We want to see what prefixes and suffixes may match. We use several if-statements.

Step 1 We use startswith on an example string. We see that the string begins with the letters "cat."

Step 2 We test a longer prefix to the string. We can use any length of string as an argument to startswith.

Step 3 We use "not startswith" to see if the string does not start with "elephant."

Step 4 Here we use the endswith method. It uses the same syntax as startswith but tests the final characters in a string.

Step 5 If we want to see if something does not match, we can test against the False constant.

phrase = "cat, dog and bird"

# Step 1: see if the phrase starts with this string.
if phrase.startswith("cat"):
    print(True)

# Step 2: a longer prefix.
if phrase.startswith("cat, dog"):
    print(True)

# Step 3: it does not start with this string.
if not phrase.startswith("elephant"):
    print(False)

# Step 4: test the end of the string.
if phrase.endswith("bird"):
    print("Ends with bird")

# Step 5: does not match.
if phrase.endswith("?") == False:
    # Does not end in a question mark.
    print(False)True
True
False
Ends with bird
False

Some notes, performance

In my performance testing, I have found Python tends to be fastest when the minimal number of statements and method calls are made.

And This means startswith and endswith are a good choice—they can keep program short and clear.

With string-testing methods like startswith and endswith, we can check the beginning and ends of strings. This can avoid complexity in code.

Startswith, endswith

Example

Some notes, performance

Startswith, `endswith`