Type Conversion

Syntax

int(x)  float(x)  str(x)  bool(x)

Examples

whole = int(9.8)     # 9  (truncates, doesn't round)
decimal = float(5)   # 5.0

print(whole, decimal)
print(round(9.8))    # 10 (round() rounds properly)

age = int("25")
price = float("19.99")
print(age + 1, price * 2)

score = 95
message = "Your score is " + str(score)
print(message)

print(bool(0))       # False
print(bool(1))       # True
print(bool(""))      # False - empty string
print(bool("hi"))    # True - non-empty string
print(bool([]))      # False - empty list
print(bool([1, 2]))  # True - non-empty list
print(bool(None))    # False

value = "abc"

try:
    number = int(value)
except ValueError:
    print(f"'{value}' is not a valid number")

Best practices

• Wrap int()/float() conversions of user-provided text in try/except, since invalid text raises a ValueError
• Remember int() truncates decimals rather than rounding - use round() first if you want proper rounding
• Know your falsy values: 0, 0.0, "", [], {}, and None are all falsy when converted with bool()
• Use str() to build messages that combine text and numbers, or use an f-string instead for cleaner syntax

At a glance

Purpose

Scripting and general-purpose applications

File extension

.py

Runs in

Python interpreter

Usually used with

Python standard library and packages

Specifications & further reading

• Python language reference

Related Python documentation