Formatting Float Output in Python: Scientific Notation and Fixed‑Point Representations

Note: All numeric values in the examples are fabricated for illustration only; the author is a Python beginner writing a tutorial for personal reference and welcomes corrections.

When a float has many digits, Python prints it in exponential (scientific) form by default. The following code calculates the mass of the Earth based on a user‑provided diameter and shows the default exponential output.

import math
m = 5.52  # density
r = float(input('请输入地球直径(km)：'))
V = 4*math.pi*r**3/3
W = m*V*1000**3
print('地球重量为', W, '吨')
#运行结果
请输入地球直径(km)：1234
地球重量为 4.344833777941348e+19 吨

The raw exponential output is often undesirable because it contains many decimal places. You can format the output to a cleaner scientific notation using either the % formatting operator or the str.format() method.

import math
m = 5.52
r = float(input('请输入地球直径(km)：'))
V = 4*math.pi*r**3/3
W = m*V*1000**3
print('地球重量为%.2e吨' % W)  # .2 limits to two decimal places
print('地球重量为{:.2e}吨'.format(W))

Both approaches produce identical results, e.g., "地球重量为4.34e+19吨".

If you need the full integer value instead of scientific notation, replace the format specifier with f (or %.f ) to output a fixed‑point representation.

import math
m = 5.52
r = float(input('请输入地球直径(km)：'))
V = 4*math.pi*r**3/3
W = m*V*1000**3
print('地球重量为%.f吨' % W)

In summary, by changing the format specifier you can switch between exponential (e) and fixed‑point (f) output: e yields scientific notation, while f yields the complete decimal value.