str.startswith

import pandas as pd

# DataFrame 예시
data = {
    'a': ['RT123', 'AB456', 'RT789', 'CD012'],
    'b': [1, 2, 3, 4]
}

df = pd.DataFrame(data)

# 'RT'로 시작하는 값 필터링
filtered_df = df[df['a'].str.startswith('RT')]

print(filtered_df)