Python Language String

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Overview

String are a Python sequence of characters. Strings are immutable, a character within a string cannot be changed in-place once the string object has been instantiated. Python 3 supports the Unicode standard, so Python 3 strings can contain characters from any written language in the world.

Quotes

String literals can be declared using four type of quotes: sigle quotes '...', double quotes "...", triple single quotes '''...''' and triple double quotes """...""".

Single and Double Quotes

s1 = 'abc'
s2 = "xyz"

Declaring string literals bounded by single and double quotes is equivalent. There are two types of quotes to make it possible to create strings that include single and double quotes: a single-quoted string allows specifying double quotes inside and a double-quoted string allows specifying single quotes inside:

s1 = 'the color is "red"'
s2 = "the shape is 'square'"

Three Single and Three Double Quotes

Multi-line string literals can be declared using three single quotes or three double quotes. The leading and training space in such strings will also be preserved. The attempt to declare multi-line string literals bounded by single or double quotes results in SyntaxError exceptions.

s1 = '''
    the color
        is
    "red"
    '''
s2 = """
    the shape
        is
    'square'
    """
print(s1)
print(s2)

The result is:

    the color
        is
    "red"


    the shape
        is
    'square'

The [] Operator and String Slices

The [] operator can be used to read strings from the sequence, but not modify the sequence. Because strings are immutable, an attempt to change a character at a specific position in string will throw an TypeError exception:

s = 'abc'
s[0] = 'x'
[...]
TypeError: 'str' object does not support item assignment

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