Calculating π in Python

We tried 2 different implementations of the following formula.
# π = 4/1 - 4/3 + 4/5 - 4/7 + 4/9 - 4/11 + ...

p = 0
for i in range(10000):
sign = 1 if (i % 2 == 0) else -1
p += sign * 4 / (2 * i + 1)
print("cal1: " + str(p))

p = 0
for i in range(0, 10000, 2):
p += 4 / (2 * i + 1) - 4 / (2 * i + 3)
print("cal2: " + str(p))

Output:
cal1: 3.1414926535900345
cal2: 3.1414926535900367