pandas assign with new column name as string : <p>I recently discovered pandas <a href="http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.assign.html" rel="noreferrer">"assign" method</a> which I find very elegant.
My issue is that the name of the new column is assigned as keyword, so it cannot have spaces or dashes in it. </p>

<pre><code>df = DataFrame({'A': range(1, 11), 'B': np.random.randn(10)})
df.assign(ln_A = lambda x: np.log(x.A))
        A         B      ln_A
0   1  0.426905  0.000000
1   2 -0.780949  0.693147
2   3 -0.418711  1.098612
3   4 -0.269708  1.386294
4   5 -0.274002  1.609438
5   6 -0.500792  1.791759
6   7  1.649697  1.945910
7   8 -1.495604  2.079442
8   9  0.549296  2.197225
9  10 -0.758542  2.302585
</code></pre>

<p>but what if I want to name the new column "ln(A)" for example?
E.g. </p>

<pre><code>df.assign(ln(A) = lambda x: np.log(x.A))
df.assign("ln(A)" = lambda x: np.log(x.A))


File "&lt;ipython-input-7-de0da86dce68&gt;", line 1
df.assign(ln(A) = lambda x: np.log(x.A))
SyntaxError: keyword can't be an expression
</code></pre>

<p>I know I could rename the column right after the .assign call, but I want to understand more about this method and its syntax.</p>
