SO Answer

import pandas as pd

def combine(df):
    combined = [] # Init empty list
    length = len(df.iloc[:,0]) # Get the number of rows in DataFrame
    i = 0
    while i < length:
        num_elements = num_elements_equal(df, i, 0, 'T') # Get the number of consecutive 'T's
        if num_elements <= 1: # If there are 1 or less T's, append only that element to combined, with the same type
            combined.append([df.iloc[i,0],df.iloc[i,1]])
        else: # Otherwise, append the sum of all the elements to combined, with 'T' type
            combined.append(['T', sum_elements(df, i, i+num_elements, 1)])
        i += max(num_elements, 1) # Increment i by the number of elements combined, with a min increment of 1
    return pd.DataFrame(combined, columns=df.columns) # Return as DataFrame

def num_elements_equal(df, start, column, value): # Counts the number of consecutive elements
    i = start
    num = 0
    while i < len(df.iloc[:,column]):
        if df.iloc[i,column] == value:
            num += 1
            i += 1
        else:
            return num
    return num

def sum_elements(df, start, end, column): # Sums the elements from start to end
    return sum(df.iloc[start:end, column])

frame = pd.DataFrame({"Type":   ["Q", "Q", "T", "Q", "T", "T", "Q"],
                   "Volume": [10,   20,  10,  10,  20,  20,  10]})
print(combine(frame))