import pandas as pd
import numpy as np

def convert_to_nparray_double(strarray):
    '''convert a string representing an array of double into a numpy array of type float64.
    '''
    if strarray.startswith('[') and strarray.endswith(']'):
        nparray = np.array(eval(strarray), dtype=np.float64)
    else:
        raise ValueError("the string array is not a list")
    return nparray

def convert_to_nparray_float(strarray):
    '''convert a string representing an array of float into a numpy array of type float32.
    '''
    if strarray.startswith('[') and strarray.endswith(']'):
        nparray = np.array(eval(strarray), dtype=np.float32)
    else:
        raise ValueError("the string array is not a list")
    return nparray

def convert_to_nparray_short(strarray):
    '''convert a string representing an array of short into a numpy array of type int16.
    '''
    if strarray.startswith('[') and strarray.endswith(']'):
        nparray = np.array(eval(strarray), dtype=np.int16)
    else:
        raise ValueError("the string array is not a list")
    return nparray

def convert_to_nparray_int(strarray):
    '''convert a string representing an array of integer into a numpy array of type int32.
    '''
    if strarray.startswith('[') and strarray.endswith(']'):
        nparray = np.array(eval(strarray), dtype=np.int32)
    else:
        raise ValueError("the string array is not a list")
    return nparray

def convert_to_nparray_long(strarray):
    '''convert a string representing an array of long into a numpy array of type int64.
    '''
    if strarray.startswith('[') and strarray.endswith(']'):
        nparray = np.array(eval(strarray), dtype=np.int64)
    else:
        raise ValueError("the string array is not a list")
    return nparray

def convert_to_nparray_bool(strarray):
    '''convert a string representing an array of boolean into a numpy array of type bool.
    '''
    if strarray.startswith('[') and strarray.endswith(']'):
        strarray = strarray.replace('f', 'False').replace('t', 'True')
        nparray = np.array(eval(strarray), dtype=bool)
    else:
        raise ValueError("the string array is not a list")
    return nparray

# The converter_map
converter_map = {
    'transit_id': convert_to_nparray_long,       # convert string array to array of long
    'g_transit_time': convert_to_nparray_double, # convert string array to array of double
    'g_transit_flux': convert_to_nparray_double, # ...
    'g_transit_flux_error': convert_to_nparray_float,
    'g_transit_flux_over_error': convert_to_nparray_float,
    'g_transit_mag': convert_to_nparray_double,
    'g_transit_n_obs': convert_to_nparray_short,
    'variability_flag_g_reject': convert_to_nparray_bool,
}

df = pd.read_csv("epoch_photometry.csv", converters=converter_map)
df.head()

# now you can access each value as usual.
df['transit_id'][8][0:10]

array([17281375268770552, 17285467545589179, 23455862064423384,
       23459954326153121, 24575690588304868, 24579782891468143,
       26219912980604604, 34116667037336254, 35461501065159748,
       37064556328564301])

# you can also get it back to astropy table
from astropy.table import Table
table = Table.from_pandas(df)
table