Casting Examples

>>> int(4.5)
4
>>> int(-4.5)
-4
>>> int(1.5e100)
14999999999999999267208920533534235242810259434158468763468571810551997532349366721768062376180973568
>>> int(1.5555555555e100)
15555555555000000634775410563936071849876978208250285056660387478653424091320529666325108209909497856
>>> bool(2.3)
True
>>> bool(0)
False
>>> int("cows")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: 'cows'
>>> str(True)
'True'
>>> str(23)
'23'
>>> str(1.5e6)
'1500000.0'
>>> x = 3.4
>>> int(x)
3

Format Strings These are preceded by an f. Expressions inside of curly braces are evaluated and droppped into the string. To make an actual curly brace, use \{.

Special Characters These are preceded by a \.

>>> print("quack\tmooo\tbaaaa")     #\t is tab
quack	mooo	baaaa
>>> print("1\n2\n3\n")              #\n is newline
1
2
3

You can get your favorite unicode characters using \uXXXX, where each X represents a hex digit.

>>> print("\u03b1")
α
>>> print("\u03b2")
β
>>> print("\u03b3")
γ
>>> print("\u03b4")
δ
>>> 

Raw StringsThese are preceded by an r. Within them, a \ is just a \. They turn off characters specialness.

>>> x = r"C\Crap\BillGates\sux"
>>> print(x)
C\Crap\BillGates\sux
>>> x = r"C\Crap\BillGates\sux\n\t"
>>> print(x)
C\Crap\BillGates\sux\n\t
>>> x = r"C:\Crap\BillGates\sux\n\t"
>>> x
'C:\\Crap\\BillGates\\sux\\n\\t'
>>> f"""{x} is the root cause
... of Microsoft's crappiness"""
"C:\\Crap\\BillGates\\sux\\n\\t is the root cause\nof Microsoft's crappiness"
>>> y = f"""{x} is the root cause
... ... of Microsoft's crappiness"""
>>> print(y)
C:\Crap\BillGates\sux\n\t is the root cause
... of Microsoft's crappiness

Triple-Quoted Strings These can span several lines.

>>> x = """This
... goes on
... and on
... and on 
... and on"""
>>> print(x)
This
goes on
and on
and on 
and on

Single quotes can be used for triple quoted string; you must use the same type of quote throughout.

String Methods

Remember, strings are immutable, so any string method actually returns a modified copy of a string. The original string is untouched.

Capitalize a string.

>>> x = "foo"
>>> x.capitalize()
'Foo'
>>> x
'foo'

Be the center of attention.

>>> x.center(40)
'                  foo                   '
>>> x.center(40, "*")
'******************foo*******************'

Note that the second optional argument can only be one character.

>>> x.center(40, "bar")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: The fill character must be exactly one character long

Time to visit count chocula.

>>> state = "mississippi"
>>> state.count("m")
1
>>> state.count("s")
4
>>> state.count("i")
4
>>> state.count("is")
2

You can say where to start or where to start or end. These arguments are optional.

>>> state.count("is", 5)
0
>>> state.count("is", 1, 5)
1

It's all right in the end.

>>> state.endswith("i")
True
>>> state.endswith("pi")
True
>>> state.endswith("ippi")
True

Here is how to find from the start.

>>> state.find("p")
8
>>> state
'mississippi'

Here is how to find from the end.

>>> state.rfind("p")
9

Goose Chase!

>>> state.rfind("quack")
-1

Verify a string contains only alpha characeters.

>>> state.isalnum()
True
>>> foo = "cats;dogs"
>>> foo.isalnum()
False

Digits...

>>> x = "2344"
>>> x.isdigit()
True
>>> x = "23 44"
>>> 
>>> x.isdigit()
False

Whitespace (\t, \n, \r (space))

>>> "\t".isspace()
True

Strip!

>>> x = "     space cadet        "
>>> x.strip()
'space cadet'
>>> x = "     space cadet      \t\t\n  "
>>> x.strip()
'space cadet'
>>> x = "     space     cadet      \t\t\n  "
>>> x.strip()
'space     cadet'

Strip the left or right.

>>> x.lstrip()
'space     cadet      \t\t\n  '
>>> x.rstrip()
'     space     cadet'

Replace. In with the new, out with the old.

>>> x = "XXX is prohibited on the premises.  You can't have XXX"
>>> x
"XXX is prohibited on the premises.  You can't have XXX"
>>> x.replace("XXX", "Likker")

Only replace one.

"Likker is prohibited on the premises.  You can't have Likker"
>>> x.replace("XXX", "Likker", 1)
"Likker is prohibited on the premises.  You can't have XXX"

>>> x = 4
>>> y = 13
>>> print(f"{x}*{y} = {x*y}")
4*13 = 52

Make us!

*
**
***
****
*****

Here are some solutions made by the class.

Solution 1, triple-quoted simplicity:

print("""
*
**
***
****
*****""")

Solution 2 \n games:

print("*\n***\n***\n****\n*****")

Solution 3, fashion-forward format foolery:

x = "*"
print(f"*\n{x*2}\n{x*3}\n{x*4}\n{x*5}")

Try these for next time!

    *
   ***
  *****
 *******
*********

     *
    * *
   * * *
  * * * *
 * * * * *
* * * * * *
    * *
    * *

Using input