Use Series.str.split
:
In [1908]: df['Symbol'] = df['Stock'].str.split('.').str[0]
In [1909]: df
Out[1909]:
Stock ROC5 ROC20 ROC63 ROCmean Symbol
0 IBGL.SW -0.59 3.55 6.57 3.18 IBGL
0 EHYA.SW 0.98 4.00 6.98 3.99 EHYA
0 HIGH.SW 0.94 4.22 7.18 4.11 HIGH
0 IHYG.SW 0.56 2.46 6.16 3.06 IHYG
0 HYGU.SW 1.12 4.56 7.82 4.50 HYGU
0 IBCI.SW 0.64 3.57 6.04 3.42 IBCI
0 IAEX.SW 8.34 18.49 14.95 13.93 IAEX
0 AGED.SW 9.45 24.74 28.13 20.77 AGED
0 ISAG.SW 7.97 21.61 34.34 21.31 ISAG
0 IAPD.SW 0.51 6.62 19.54 8.89 IAPD
0 IASP.SW 1.08 2.54 12.18 5.27 IASP
0 RBOT.SW 10.35 30.53 39.15 26.68 RBOT
0 RBOD.SW 11.33 30.50 39.69 27.17 RBOD
0 BRIC.SW 7.24 11.08 75.60 31.31 BRIC
0 CNYB.SW 1.14 4.78 8.36 4.76 CNYB
0 FXC.SW 5.68 13.84 19.29 12.94 FXC
0 DJSXE.SW 3.11 9.24 6.44 6.26 DJSXE
0 CSSX5E.SW -0.53 5.29 11.85 5.54 CSSX5E
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