String Special Cases

String Special Cases#

Note

Source: Escape sequences table drawn directly from the SE4ML Python chapter (chapter_python.rst, lines 2356–2413). Raw strings, multiline strings, and the in operator section are adapted from the SE4ML presentation.

Escape Sequences#

Some characters cannot be typed directly inside a string literal. Python uses escape sequences — a backslash followed by a character — to represent them:

Sequence

Meaning

\\

Literal backslash

\'

Single quote

\"

Double quote

\n

Newline (line feed)

\t

Tab

\r

Carriage return

\0

Null character

 
>>> print("Line one\nLine two")
Line one
Line two

>>> print("Column 1\tColumn 2")
Column 1     Column 2

>>> print("She said, \"Hello.\"")
She said, "Hello."

Raw Strings#

If you need a string that contains many backslashes — such as a Windows file path — a raw string treats backslashes as literal characters. Prefix the opening quote with r:

>>> path = r"C:\Users\student\Documents"
>>> print(path)
C:\Users\student\Documents

Without the r, \U, \s, and \D would be interpreted as escape sequences (and either produce unexpected characters or errors).

Multiline Strings#

Triple-quoted strings can span multiple lines and preserve all whitespace, including newlines:

message = """Dear student,

Welcome to Introduction to Computer Science.

Regards,
The Department"""

print(message)

Output:

Dear student,

Welcome to Introduction to Computer Science.

Regards,
The Department

Triple-quoted strings are also used as docstrings — documentation attached to functions and classes. We will see those in the Functions chapter.

Testing for Substrings#

The in operator tests whether one string is a substring of another:

>>> "cat" in "concatenate"
True
>>> "dog" in "concatenate"
False
>>> "not" not in "certainly"
True