![]() ![]() One way to solve this problem is to enclose the string with double quotation marks rather than single quotation marks. However, the single quote in the word “it’s” would confuse Python, making it think the string had ended early. For example, let’s say you want to print the message, “It’s a trap.” We know Python uses the single quote character to define the limits (or delimit) of a string of text. When I first saw how strings worked in Python, I wondered how to enter text containing a single quote. The same thing happens if you put a number into the customer_name variable. Personally, I don’t like this behavior, but it is just the way that Python works. Instead, Python discards the old, numeric version of the variable and makes a new variable that holds a string. The statement is trying to put a string into a variable that Python has created to hold a number. You might think that this statement should generate an error. Now try this: > customer_age_in_years= 'Fred' If we try to do something silly with our variables, there is a good chance that Python will notice. ![]() Python doesn’t know how to add an integer and a string, so this error is Python’s response. Python checks to make sure the operands (the elements on each side of the + operator) make sense. We saw the same kind of error when we tried to add a string to a number in Chapter 2. TypeError: unsupported operand type(s) for +: 'int' and 'str' The following code adds these two variables. The second is called customer_name and holds the string 'Fred'. ![]() The first is called customer_age_in_years and holds the integer value 25. Start by entering the above two lines into the Python Shell part of IDLE. We can use the Python Shell part of IDLE to experiment with string and number variables > customer_age_in_years = 25 Ht1528 - Enabling and using the 'root' user in macOS.Python keeps track of the contents of each variable and will not allow them to be combined incorrectly. If ^D doesn't work, type 'stty -a' to see what the eof character is. The special parameters * and have special meaning when in double quotes.Įnd Of File is usually CTRL+D (^D) when input is from the keyboard. A double quote may be quoted within double quotes by preceding it with a backslash. Backslashes preceding characters without a special meaning are Within double quotes, backslashes that are followed by one of these characters are removed. The backslash preceding the ! is not removed. If enabled, history expansion will be performed unless an ! appearing in double quotes is escaped using a backslash. ![]() Retains its special meaning only when followed by one of the following characters: $, `, ", \, or newline. The characters $ and ` retain their special meaning within double quotes. Single quotes, even when preceded by a backslash.Įnclosing characters in double quotes ( ") preserves the literal value of all characters within the quotes, with the exception of $, `, and \ and, when history expansion is enabled, !. Single QuotesĮnclosing characters in single quotes ( ') preserves the literal value of every character within the quotes. (that is, it is removed from the input stream and effectively ignored). If a \newline pair appears, and the backslash itself is not quoted, the \newline is treated as a line continuation It preserves the literal value of the next character that follows, with the exception of newline. Escape CharacterĪ non-quoted backslash \ is the Bash escape character. Whenever you pass a variable to a command, you should probably quote it.Įach of the shell metacharacters has special meaning to the shell and must be quoted if it is to represent itself. To prevent reserved words from being recognized as such, and to prevent parameter expansion. Quoting can be used to disable special treatment for special characters, Quoting is used to remove the special meaning of certain characters or words to the shell. How-to: Escape Characters, delimiters and Quotes Quoting ![]()
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