Looping over dataframe and selecting rows based on substring in Pandas

Question

I have a dataframe with 5 columns, one of which is 'TABLE_NAME'. That column has values such as:

A_value1
B_value1
B_value2
A_value150

I want to print those that start with 'A_' only.

I tried this but its returning the following:

ValueError: The truth value of a DataFrame is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

Here is the code:

value = 'A_'
for index, row in df.iterrows():
    if df.loc[df['TABLE_NAME'].str.contains(value)]:
        print('y')
    else:
        print('n')

Answer 1

You can use str.startswith:

df.loc[df.TABLE_NAME.str.startswith('A_')]

If you want to use your for loop, you can do:

value = 'A_'
for index, row in df.iterrows():
    if row['TABLE_NAME'].startswith(value):
        print('y')
    else:
        print('n')