def main() -> None:
x = int(3)
y = float(3.3)
# converting from float to string
z = int(float(3.3))
print(z)32 - Data Types
python
Numerical types
FP precision problem and Decimal
The problem with floating point (FP) number is precision.
def main() -> None:
sum = 0.1 + 0.1 + 0.1
expected = 0.3
print(f"sum = {sum}, expected = {expected}")
assert sum == expected
if __name__ == "__main__":
main()sum = 0.30000000000000004, expected = 0.3--------------------------------------------------------------------------- AssertionError Traceback (most recent call last) Cell In[2], line 9 5 print(f"sum = {sum}, expected = {expected}") 6 assert sum == expected 7 8 if __name__ == "__main__": ----> 9 main() Cell In[2], line 6, in main() 2 sum = 0.1 + 0.1 + 0.1 3 expected = 0.3 4 5 print(f"sum = {sum}, expected = {expected}") ----> 6 assert sum == expected AssertionError:
In this case, it’s better to use Decimal type:
from decimal import Decimal
def main() -> None:
sum = Decimal('0.1') + Decimal('0.1') + Decimal('0.1')
expected = Decimal('0.3')
print(f"sum = {sum}, expected = {expected}")
assert sum == expected
if __name__ == "__main__":
main()sum = 0.3, expected = 0.3Text types
# Strings can be surrounded by either single or double quotation marks
single_quoted_string = 'Hello, World!'
double_quoted_string = "Hello, World!"
# Strings using single or double quotes interchangeably
print(single_quoted_string)
print(double_quoted_string)
# Multi-line strings using triple quotes
multi_line_string = """This is a multi-line string.
It spans multiple lines.
This is often used for documentation."""
print(multi_line_string)
# Strings behave like lists: slicing, concatenation, and searching
# Slicing
substring = single_quoted_string[0:5]
print("Sliced string:", substring)
# Concatenation
concatenated_string = single_quoted_string + " How are you?"
print("Concatenated string:", concatenated_string)
# Searching
search_result = "World" in single_quoted_string
print("Searching for 'World':", search_result)
#Reassigning string
single_quoted_string = 'Goodbye, World!'
print("Reassigned string:", single_quoted_string)
# Python treats single characters and strings of characters as the same type
single_character = 'A'
print("Type of single_character:", type(single_character))
print("Type of single_quoted_string:", type(single_quoted_string))Hello, World!
Hello, World!
This is a multi-line string.
It spans multiple lines.
This is often used for documentation.
Sliced string: Hello
Concatenated string: Hello, World! How are you?
Searching for 'World': True
Reassigned string: Goodbye, World!
Type of single_character: <class 'str'>
Type of single_quoted_string: <class 'str'>f-strings
# Define variables for demonstration
product_name = "Laptop"
quantity = 3
unit_price_cents = 79999 # Unit price in cents
print(f"{product_name=}, {quantity=}, {unit_price_cents=}")
# Using f-strings to create a formatted string
summary = f"Product: {product_name}, Quantity: {quantity}, Total Price: ${(quantity * unit_price_cents) / 100:.2f}"
print(summary)
# Example of using f-strings for dynamic expressions
tax_rate = 0.07 # 7% tax rate
total_cost_cents = quantity * unit_price_cents
total_cost_with_tax = total_cost_cents * (1 + tax_rate)
# Formatting the total cost with tax using f-strings
formatted_total_cost = f"Total Cost (with tax): ${total_cost_with_tax / 100:.2f}"
print(formatted_total_cost)
# Comparison without using personal details
feature = "battery life"
hours = 10
# Demonstrating use of f-strings for including variable values and expressions
feature_description = f"The {product_name} has a {feature} of up to {hours} hours."
print(feature_description)
# Type of f_strings are still strings
print(type(feature_description))product_name='Laptop', quantity=3, unit_price_cents=79999
Product: Laptop, Quantity: 3, Total Price: $2399.97
Total Cost (with tax): $2567.97
The Laptop has a battery life of up to 10 hours.
<class 'str'>Limited-state types
def main() -> None:
# True acts as 1, False acts as 0
result = True + True # Equals 2
zero = True * False # Equals 0
print(f"result: {result}, zero: {zero}")
print(f"zero: {zero}")
options = ['False option', 'True option']
choice = options[True] # Selects 'True option'
print(f"choice: {choice}")
denominator = 0
numerator = 10
safe_division = denominator and numerator / denominator
print(f"safe_division: {safe_division}")
number = 10
result = "Positive" if number >= 0 else "Negative"
NOT = not True # False
AND = True and False # False
OR = True or False # True
print(f"NOT: {NOT}, AND: {AND}, OR: {OR}")
truthy_count = sum([True, False, True, 1 == 1, False]) # 3
print(f"truthy_count: {truthy_count}")
x = 5
is_valid_range = 1 <= x <= 10
print(f"is_valid_range: {is_valid_range}")
if __name__ == "__main__":
main()result: 2, zero: 0
zero: 0
choice: True option
safe_division: 0
NOT: False, AND: False, OR: True
truthy_count: 3
is_valid_range: TrueEnumerator data type
from enum import Enum
class EmployeeType(Enum):
FULL_TIME = 1
PART_TIME = 2
CONTRACTOR = 3
def main() -> None:
x = int(float(3.3))
e_type = EmployeeType.FULL_TIME
print(e_type)
print(e_type.value)
if __name__ == "__main__":
main()EmployeeType.FULL_TIME
1Or we can use the auto function so that we do not have to hard-code the values:
from enum import Enum, auto
class EmployeeType(Enum):
FULL_TIME = auto()
PART_TIME = auto()
CONTRACTOR = auto()
def main() -> None:
x = int(float(3.3))
e_type = EmployeeType.FULL_TIME
print(e_type)
print(e_type.value)
if __name__ == "__main__":
main()EmployeeType.FULL_TIME
1Or we can use StrEnum so that the value is not arbitrary number but using string to be more explicit:
from enum import StrEnum, auto
class EmployeeType(StrEnum):
FULL_TIME = auto()
PART_TIME = "4_hour_shift" # we can manually define if we want to
CONTRACTOR = auto()
def main() -> None:
x = int(float(3.3))
ft_e_type= EmployeeType.FULL_TIME
pt_e_type = EmployeeType.PART_TIME
print(ft_e_type.value)
print(pt_e_type.value)
if __name__ == "__main__":
main()full_time
4_hour_shift