This module includes:

1. Values

Python has several basic types of values. The most common include:

  • Strings (text)
  • Integers (whole numbers)
  • Floats (decimal numbers)
  • Booleans (True and False)
  • None (represents “no value”)

▷ Strings

Strings are sequences of characters interpreted as text. They are enclosed in single or double quotes:

s1 = "Hello, world!"
s2 = 'Rock & Roll'

  • Arithmetic with strings?

    "9" + "3"      # → "93"
"9" + 3        # TypeError: can’t add str and int

  • Common string operations

    # Concatenation
"Hello, " + "Python!"     # → "Hello, Python!"

# Length
len("NLTK")               # → 4

# Indexing
s = "Python"
s[0]                      # → "P"
s[-1]                     # → "n"

    Integers

Integers are whole numbers without a decimal point:

i1 = 1
i2 = 42
i3 = -7

  • Basic arithmetic

    i1 + i2                   # → 43
i2 - 10                   # → 32
i3 * 3                    # → -21

# Division in Python 3
7 / 2                     # → 3.5   # true division
7 // 2                    # → 3     # floor division

▷ Floats

Floats are numbers with decimal places:

f1 = 1.234
f2 = 2.0
f3 = -6.789

  • Mixing ints and floats

    3 + 0.5                   # → 3.5
7 / 2                     # → 3.5

▷ Booleans

Booleans represent truth values: True or False.

is_hungry = True
is_sleepy = False
  • Used in comparison
5 > 3        # → True
2 == 4       # → False
  • More about comparison operators
Operator Meaning Example Result
== Equal to 2 == 2 True
!= Not equal to 3 != 4 True
<, >, <=, >= Less than, greater than, etc. 5 >= 2 True

Example with !=:

if [] != [None]:
    print("These are different")
# Output: These are different
  • Boolean logical operators:
Operator Description Example Result
and True if both are True True and False False
or True if at least one is True True or False True
not Reverses the Boolean value not True False 
x = True
y = False

x and y       # → False
x or y        # → True
not x         # → False

▷ None

None is a special value that means “no value” or “nothing.” It’s often used as a default or placeholder.

result = None
print(result)        # → None

2. Variables

Variables store values of any type. Assignment is straightforward:

a = "this is a string"
b = 9
c = 3.2

print(b + c)                # → 12.2

  • Reassignment

    a = a + "!"
print(a)                   # → "this is a string!"

3. Functions

Functions perform operations on values or objects. Common ones include:

Function Description Example
print(x) Display x in the console print("Hi!") → Hi!
len(x) Return length of a string or list len("abc") → 3
str(x) Convert x to a string str(16) → "16"
int(x) Convert to integer (floats rounded down) int(3.9) → 3
float(x) Convert to float float("2.5") → 2.5

4. Methods

Methods are functions bound to objects (typically defined inside a class). For strings:

sample = "This is a STRING"

  • .lower()

    sample.lower()            # → "this is a string"
# str.split(sep) – Splits a string into a list of substrings, using sep (separator) as the delimiter.

  • .split(sep)

    sample.lower().split(" ")
# → ['this', 'is', 'a', 'string']
# If sep is given → the string is split wherever that exact substring occurs.
# If sep is omitted or set to None → the string is split on whitespace (spaces, tabs, newlines).

  • Splitting on another character

    "banana".split("a")       # → ['b', 'n', 'n', '']

  • Combining functions & methods

Chain calls for concise code:

# Lowercase, split into words, and count them
len("This is a STRING".lower().split())   # → 4

5. Exercises

  1. Assign

    # Assign a sentence that is relevant to you, for example, I wrote,
  string_sent = "I like running trails and drinking cold brew."

  2. Count characters

    print(len(string_sent))

  3. Split into words

    list_sent = string_sent.split(" ")
print(list_sent)

  4. Count words

    print(len(list_sent))

  5. Average characters per word

    av_chars = len(string_sent) / len(list_sent)

  6. Print as string

    print(str(av_chars))