## Bar charts with error bars using Python and matplotlib

Bar charts with error bars are useful in engineering to show the confidence or precision in a set of measurements or calculated values. Bar charts without error bars give the illusion that a measured or calculated value is known to high precision or high confidence. In this post, we will build a bar plot using Python and matplotlib. The plot will show the coefficient of thermal expansion (CTE) of three different materials based on a small data set. Then we'll add error bars to this chart based on the standard deviation of the data.

## Unicode characters for engineers in Python

Unicode characters are very useful for engineers. A couple commonly used symbols in engineers include Omega and Delta. We can print these in python using unicode characters. From the Python interpreter we can type:

>>> print('Omega: \u03A9')
Omega: Ω
>>> print('Delta: \u0394')
Delta: Δ
>>> print('sigma: \u03C3')
sigma: σ
>>> print …