String Objects

Defining String Objects

Strings in Python are ordered sequences of characters arranged neatly, like a series of letters forming words or sentences. Imagine a string like a necklace of beads where each bead represents one character.

Strings have three main characteristics you need to understand:

1. Ordered character sequence - each character has a fixed position
2. Enclosed in quotes - can be single or double quotes
3. Type str - Python recognizes this as a string data type

# Example string with single quotes>>> 'hello''hello'# Example string with double quotes  >>> "hello"'hello'# Displaying string with print>>> print("hello")hello# Storing string in a variable>>> text = 'hello'>>> text'hello'

Notice that when you type a string in Python, the output will always display single quotes even if you use double quotes. However, when using print(), the string is displayed without quotes.

Empty Strings and str() Function

Python allows you to create empty strings and convert other data types to strings.

Empty Strings

Empty strings are like empty containers ready to be filled with characters. You can create them with quotes containing nothing.

# Creating an empty string>>> str = "">>> str''

str() Function

The str() function acts like a translator that converts various data types into string form. This is very useful when you need to convert numbers to text.

# Converting number to string>>> str(5)'5'# Converting float to string>>> xstr = str(3.4)>>> print(xstr)3.4

Multi-line Strings

When you need to write long text or text consisting of multiple lines, Python provides several ways to handle it.

Line Continuation Character

You can use the backslash (\) character to continue a string to the next line. This is useful when a string is too long for one line.

# Using backslash for line continuation>>> text = 'xxx' ...: 'yyy'>>> text'xxxyyy'>>> print(text)xxxyyy

Line Continuation with Parentheses

Another alternative is using parentheses to group multi-line strings. This method is often more readable.

# Using parentheses for line continuation>>> text = ('xxx'...: 'yyy')>>> text'xxxyyy'>>> print(text)xxxyyy

Triple Quotes

Triple quotes (three quote marks) allow you to write strings that are truly multi-line with actual line breaks.

# Triple single quotes>>> text = '''xxx...: yyy...: zzz'''>>> text'xxx\nyyy\nzzz'>>> print(text)xxxyyyzzz

Triple double quotes work the same way as triple single quotes, providing flexibility in quote selection.

String Literal Concatenation

Python provides several ways to combine strings, both literals and variables.

Adjacent Literal Concatenation

When you place string literals next to each other without operators, Python will automatically combine them. This is like joining two words without needing glue.

# Adjacent string literals are automatically combined>>> 'hello ' 'world''hello world'# Combining multiple strings at once>>> "hel" 'lo' " world" '!''hello world!'

Plus Operator (+)

The plus operator functions like glue that combines strings into one unit.

# Using + operator for concatenation>>> 'hello ' + 'world''hello world'

Multiplication Operator (*)

The multiplication operator allows you to repeat a string as many times as desired, like copying text multiple times.

# Repeating string with * operator>>> 3 * '+o+''+o++o++o+'

String Variable Concatenation

When working with string variables, there are special rules you need to understand.

Using Operators

To combine strings stored in variables, you must use the + or * operators. Unlike string literals, variables cannot be combined just by placing them adjacent to each other.

# Defining string variables>>> text1 = 'hello'>>> text2 = 'world!'>>> text3 = '+o+'>>> a = 3# Combining with + operator>>> text1 + ' world''hello world!'>>> 'hello ' + text2'hello world!'>>> text1 + ' ' + text2'hello world!'# Repeating with * operator>>> a * text3'+o++o++o+'>>> text3 * a'+o++o++o+'

Common Errors

It's important to understand that placing string variables adjacent without operators will cause syntax errors.

# ERROR: Cannot combine variables without operators>>> text1 'world'SyntaxError ...>>> 'hello ' text2SyntaxError ...>>> text1 text2SyntaxError ...