how to creating strings of characters in python

how to creating strings of characters in python

From email readers and web browsers to calendars and games, text plays a central role in computer programs. This chapter introduces a non-numeric data type that represents text, such as the words in this sentence or the sequence of bases in a strand of DNA. Along the way, we will see how to make programs a little more interactive by printing messages to our programs users and getting input from them.

Creating Strings of Characters :

Computers may have been invented to do arithmetic, but these days, most of them spend a lot of their time processing text. Many programs create text, store it, search it, and move it from one place to another. In Python, text is represented as a string, which is a sequence of characters (letters, digits, and symbols). The type whose values are sequences of characters is str. The characters consist of those from the Latin alphabet found on most North American keyboards, as well as Chinese morphograms, chemical symbols, musical symbols, and wuch nore. In Python, we indicate that a value is a string by putting either single or double quotes around it. As we will see in Section 4.2, Using Special Characters in Strings, on page 68, single and double quotes are equivalent except for strings that contain quotes. You can use whichever you prefer. (For docstrings, the Python style guidelines say that double quotes are preferred.)

Here are two examples:

>>> 'Aristotle' 'Aristotle' >>> "Isaac Newton" 'Isaac Newton

The opening and closing quotes must match:

Working with Text * 66

>>> 'Charles Darwin" File "<stdin>", line 1

Charles Darwin"

syntax error: EOL while scanning string literal

error above indicates that the end of the EOL stands for "end of the line." The error above indicates that line was reached before the end of the string (which should be marked with a closing single quote) was found.

acters limited only by computer memory.

Strings can contain any number of characters, limited only by computer The shortest string is the an empty string, containing no characters at a

Operations on Strings

  Python has a built-in function, len, that returns the number of characters between the opening and closing quotes: >>> len ('Albert Einstein') 15 >>> len('123')

>>> len(' ')

>>> len('')

We can add two strings using the + operator, which produces a new string containing the same characters as in the two operands:

>>> 'Albert' + ' Einstein' 'Albert Einstein'

When + has two string operands, it is referred to as the concatenation operator. Operator + is probably the most overloaded operator in Python. So far, we've applied it to integers, floating-point numbers, and strings, and we'll apply it to several more types in later chapters.

As the following example shows, adding an empty string to another string produces a new string that is just like the nonempty operand:

>>> "Alan Turing" + " 'Alan Turing' >>>" + 'Grace Hopper' 'Grace Hopper

report erratum. discus