我有以下代码需要一个多小时才能运行。我相信它变慢的原因是附加数据帧是一项占用大量内存的操作。 有什么办法可以改善它，使其在更大的数据集（即> 25MB）上更快？

df = pd.DataFrame(columns = ["X1","NumHelpfulVotes","NumVotes","Product_ID","Rating","ReviewLength","numExclamations","HelpfulFraction"])

filename = "Reviews.txt"

#open file and read all the lines
file = open(filename,"r",encoding = "latin-1")
lines = file.readlines()
file.close()

#track index of item
index = 0

#loop through all the lines
#each new entry starts every 9 lines
for i in range(0,len(lines),9):

    #get product ID
    info_start = lines[i].index(":") + 1
    product_id = lines[i][info_start:].strip() #get the text after the colon and strip white space

    #get helpfulness data
    info_start = lines[i+3].index(":") + 1 
    helpfulness_data = lines[i+3][info_start:].strip() #get text after colon and clear whitespace

    info_start = helpfulness_data.index("/")
    numVotes = int(helpfulness_data[info_start+1:]) #get number after /
    numHelpful = int(helpfulness_data[:info_start]) #get number before /

    #get rating
    info_start = lines[i+4].index(":") + 1
    rating = float(lines[i+4][info_start:]) #get number after colon

    #review data
    info_start = lines[i+7].index(":") + 1
    review = lines[i+7][info_start:].strip() #get all the text in the review

    review_len = len(review)
    num_exclamations = review.count("!") #count the number of exclamations

    if numVotes == 0:
        helpful_fraction = pd.np.nan
    else:
        helpful_fraction = numHelpful/numVotes

    #append data to df
    df.loc[len(df)]=[index,numHelpful,numVotes,product_id,rating,review_len,num_exclamations,helpful_fraction]

    #increment index
    index +=1


df.head()``