Up to now, a print statement has output either a fixed piece of text or the contents of a single variable. Concatenation lets you join those pieces together, so that one line of output can mix fixed text with information that is stored in variables.

Joining with +

Put a + between two strings and Python sticks them together into one longer string:

print("Hello " + "world")

Hello world

A variable name can go on either side of the +. Python looks inside the variable first, and then joins the contents to the rest:

name = "Andy"

print("Your name is " + name)

Your name is Andy

The + symbols and the variable names stay outside the speech marks. Everything inside speech marks is treated as plain text, so print("Your name is + name") would output the literal characters Your name is + name.

Spaces do not appear by themselves

Concatenation joins the strings exactly as they are written, with nothing inserted in between. If you want a space between two pieces, you have to write that space yourself, inside one of the strings:

first_name = "Andy"
last_name = "Colley"

print(first_name + last_name)
print(first_name + " " + last_name)

AndyColley
Andy Colley

The " " in the second print is a string that contains nothing but a single space. It is easy to forget, and a missing space is the most common reason a concatenated sentence comes out looking wrong.

The result of a concatenation does not have to be output straight away. You can assign it to a variable of its own and use that variable later:

first_name = "Andy"
last_name = "Colley"
full_name = first_name + " " + last_name

print(full_name)

Andy Colley

Numbers need str()

The + symbol means two different things in Python. Between two strings it joins them together; between two numbers it adds them up. When you mix the two, Python refuses to guess which one you meant and stops with a TypeError:

number = 7

print("You picked number " + number)

The fix is str(), which makes a string version of the value so that it can be concatenated like any other piece of text:

number = 7

print("You picked number " + str(number))

You picked number 7

str(number) does not change what is stored in number. It only produces a string copy for use in that one line, and the variable itself still holds the number 7.

Try it yourself

Run the code below. Then try removing the " " from the first print, or the str() from the second, and run it again to see what each of them was doing.

first_name = "Andy"
last_name = "Colley"
age = 12

print(first_name + " " + last_name)
print("You are " + str(age) + " years old.")