The words This is a message. is called a string literal. Literal in this context means that sequence of characters makes up the value of the string stored in the variable, message in this case.

Important Note: Strings are immutable in Python.

Concatenation occurs when we combine two or more strings together to make one string. We do this in Python using the plus-sign (+) operator. Notice that's the same operator we use with numeric values for addition, so we can think of concatenation as adding strings together.

Here's an example using string literals (read the code comments for details):

# We can concatenate string literals, like this ...
print("Bob" + "Smith")
# ... notice though that when you run this it prints
# BobSmith, with no space. We need to include any
# punctuation or spaces in the string literal ...
print("Bob " + "Smith")
# ... Note that now we included a space in the first
# string literal, so now the output will be
# Bob Smith, which is more command and readable.

# First we'll prompt the user for their first
# and last names and store the values the
# enter in variables...
first_name = input("Enter your first name: ")
last_name = input("Enter your last name: ")
# ... then we'll print the first and last
# names concatenating them together using the
# + operator...
print(first_name + last_name)
# ... we have the same problem in this example
# as we did in the previous example, it prints
# the first and last name with no space between
# them. We need to include punctuation and
# spaces with variable-based output as well,
# like this ...
print(first_name + " " + last_name)
# ... note that we are concatenating the first
# name, a string literal containing only a single
# space and the last name.

There are times when we need to access individual characters in a string, we do this based on an index (position) of characters in the string. If we think of a string as a sequence of individual alphanumeric characters we can assign a number to each character (called an index). In Python, indexes for strings start at zero.

Let's look at an example:

print(full_name[2])

b

print(full_name[-4])

m

Another way we can access portions of a string is through slicing. Slicing allows us to select a range of characters within a string. The syntax is similar to using an index as shown above, but now we add the colon operator : and provide another index value after the colon, like this:

print(full_name[2:7])

print(full_name[2:5])

print(full_name[1:5])

print(full_name[3:5])

print(full_name[1:])

print(full_name[:5])

print(full_name[:3])

print(full_name[:-6])

print(full_name[4:])

print(full_name[-5:])

print(full_name[:])

The Python string data type has a set of useful built-in methods that we can use to work with strings. We will take a look at a few of them for now, and then explore additional string methods as we progress. There is a full list of the string methods here (opens in a separate tab).

str_var_1 = "Bob"
str_var_2 = "Bob123"
str_var_3 = "Bob Smith"
print(str_var_1.isalpha())
print(str_var_2.isalpha())
print(str_var_3.isalpha())

str_var_1 = "Bob"
str_var_2 = "Bob123"
str_var_3 = "Bob Smith"
print(str_var_1.lower())
print(str_var_2.lower())
print(str_var_3.lower())

str_var_1 = "Bob"
str_var_2 = "Bob123"
str_var_3 = "Bob Smith"
print(str_var_1.upper())
print(str_var_2.upper())
print(str_var_3.upper())

str_var_1 = "this is a sentence."
print(str_var_1.capitalize())

str_var_1 = "this is a sentence."
print(str_var_1.title())

str_var_1 = "this is a sentence."
print(str_var_1.replace("s", "Z"))
print(str_var_1.replace("s", "ZZZ"))
print(str_var_1.replace("s", "ZZZ", 1))

As indicated previously, Python contains several built-in functions that are more general-purpose (not only useful with strings), like print(). We can use many of these functions with strings as well. There is a full list of the string methods here (opens in a separate tab). Let's look at one example for now and we'll learn more later.

str_var_1 = "Bob"
print(len(str_var_1))
str_var_1 = "This is a sentence."
print(len(str_var_1))
str_var_1 = "This is a longer sentence that is about nothing of any particular importance."
print(len(str_var_1))
str_var_1 = "Address: 123 Nowhere Street, SLC, UT 84999"
print(len(str_var_1))

When we are working on programs that print to the screen we want to present the output in a user-friendly and readable form. The Python console is non-graphical, meaning it does not display colors, graphics, images, etc. But we often will generate output that is not just the result of calculations or processing, but we add text formatting to make it look formatted and even artistic. Here are a few examples:

print(u'\u00A9')
print(u'\u00BD')
print(u'\u00F1')
print(u'\u0376')
print(u'\u2600')
print(u'\u259A')
print(u'\u259A' * 30, end="")
print()
print(u'\u2550' * 30)
print("Main Menu")
print(u'\u2550' * 30)
print("1. Menu Option 1")
print("2. Menu Option 2")
print("3. Menu Option 3")
print("4. Exit")
print(u'\u2550' * 30)
print("User Prompt: ")
print(u'\u2550' * 30)

Code Details:

• Lines 1 thru 6 use the u'\u____' syntax to print characters from Unicode that are not found on the standard keyboard.
• The code in the print statement, like 00BD is found in the list of Unicode characters here
• Line 7 uses the * operator to repeat the character a specified number of times.
• Line 8 prints a blank line.
• Lines 9 thru 18 use Unicode characters for the lines, which look better than our example menu shown earlier (above) that uses dash characters to draw lines.