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Reproducible Example

import numpy as np
import pandas as pd

c_names = ["a.1", "b", "c", "d"]
df = pd.DataFrame(np.random.randn(100, 4), columns=c_names)
df.eval("f.1 = a.1 + 5")

Issue Description

Raises following exception: 

f .1 =a .1 +5
SyntaxError: invalid syntax

this applies to all prohibited characters in variable names. I have some "bicycle" solution for this issue (for "." only) for now:

def apply_formulas(data, formulas):
    literal = "arxhdkl_wqmasmdvcalsnd"
    columns = [name.replace(".", literal) for name in data.columns]
    data.columns = columns

    for formula in formulas:
        f = formula.replace(".", literal)
        data.eval(f, inplace=True)

    columns = [name.replace(literal, ".") for name in data.columns]
    data.columns = columns
    return data

I think that the problem lies in the fact that something like this happens inside the method:

df.f.1 = df.a.1 + 5

instead

df["f.1"] = df["a.1"] + 5

Expected Behavior

df.eval("f.1 = a.1 + 5")

I hope DataFrame.eval() will supports equation like below

Installed Versions

INSTALLED VERSIONS ------------------ commit : 66e3805b8cabe977f40c05259cc3fcf7ead5687d python : 3.8.10.final.0 python-bits : 64 OS : Linux OS-release : 5.10.147+ Version : #1 SMP Sat Dec 10 16:00:40 UTC 2022 machine : x86_64 processor : x86_64 byteorder : little LC_ALL : None LANG : en_US.UTF-8 LOCALE : en_US.UTF-8 pandas : 1.3.5 numpy : 1.22.4 pytz : 2022.7.1 dateutil : 2.8.2 pip : 22.0.4 setuptools : 57.4.0 Cython : 0.29.33 pytest : 3.6.4 hypothesis : None sphinx : 3.5.4 blosc : None feather : 0.4.1 xlsxwriter : None lxml.etree : 4.9.2 html5lib : 1.0.1 pymysql : None psycopg2 : 2.9.5 (dt dec pq3 ext lo64) jinja2 : 3.1.2 IPython : 7.9.0 pandas_datareader: 0.9.0 bs4 : 4.6.3 bottleneck : None fsspec : 2023.1.0 fastparquet : None gcsfs : None matplotlib : 3.5.3 numexpr : 2.8.4 odfpy : None openpyxl : 3.0.10 pandas_gbq : 0.17.9 pyarrow : 9.0.0 pyxlsb : None s3fs : None scipy : 1.10.1 sqlalchemy : 1.4.46 tables : 3.7.0 tabulate : 0.8.10 xarray : 2022.12.0 xlrd : 1.2.0 xlwt : 1.3.0 numba : 0.56.4

Comment From: ritikBhandari

Hi @RinnetenseiQ,

So the problem with the code is that the column name "a.1" contains a period (.) character, which is a special character in pandas when used in column names. The period is used to separate levels in a hierarchical index.

If you want to use such names in the column, you need to enclose the column name in backticks to indicate that it is a literal column name.

Like this df.eval("`a.1`+5")

And also, eval() method does not create new columns in the original DF unless the expression is explicitly designed to do so. You can use this expression for much clarity though:

df["f.1"] = df["a.1"] + 5

Comment From: topper-123

Yes, like @ritikBhandari says, the dot is used to access attributes, so if it exists in a name, the fix is to surround the name by backticks.

I'm closing this issue as wontfix.