Keep trailing zeroes in python

Question

I am writing a class to represent money, and one issue I\'ve been running into is that \"1.50\" != str(1.50). str(1.50) equals 1.5, and alll of a sudden, POOF.

Answer 1

The proposed solutions do not work when the magnitude of the number is not known in advance, which is common in scientific applications rather than in money-related ones. I give an alternative solution for those, like me, coming to this question looking for the scientific case.

For example, if I want to print x = 1.500e-4 to three significant digits (common situation when dealing with measurements with a given uncertainty), the following command obviously does not give the correct result:

x = 1.500e-4
print(f"{x:.3f}")

----> 0.000

Here I used the modern Python 3.6+ f-strings for the formatting.

One may think of using the g format specifier, but this also does not give the desired result to three significant digits as the trailing zero is omitted:

x = 1.500e-4
print(f"{x:.3g}")

----> 0.00015

The correct answer can be obtained using the g format specifier together with a rather obscure option, the hash character #, of the format-specification mini language, in the following way:

x = 1.500e-4
print(f"{x:#.3g}")

----> 0.000150

This formatting also works unchanged in the simpler case of the original question:

x = 1.500
print(f"{x:#.3g}")

----> 1.50