Python Type Conversion: int(), float(), str(), bool()

Explicit Conversion

int("42")       # 42
float("3.14")   # 3.14
str(100)        # "100"
bool(0)         # False
bool("")        # False
bool("abc")     # True

Implicit Conversion

Python auto-promotes int → float in mixed arithmetic:

3 + 0.5   # 3.5 (float)

Common Errors

int("3.14")      # ValueError — use float first
int("abc")       # ValueError
int(" 42 ")      # 42 (whitespace OK)
float("inf")     # infinity
float("nan")     # not-a-number

Safe Pattern

def to_int(s, default=0):
    try:
        return int(s)
    except ValueError:
        return default

Truthy and Falsy

Empty collections, 0, 0.0, "", and None are all falsy. Everything else is truthy.