python CSV 文件的读写

1.CSV文件

import csv

with open(r"E:\code\0_DataSet\tianchi_2015_mobile_recommand\fresh_comp_offline\tianchi_fresh_comp_train_user.csv","r+") as rdFile ,\
    open("data.csv","w+",newline="") as wrFile:
        # writeFile must open with newline+="" or blank line will appear
        #1 create reader & writer
        csvReader = csv.reader(rdFile)
        csvWriter = csv.writer(wrFile)
        #2 get the headmost 10000 line and write into wrFile
        for line,i in zip(csvReader,range(10001)):
           csvWriter.writerow(line)

CSV 文件的读写:

　　① open()

　　　　写入必须用 指定参数 newline=""

　　②创建 reader() | writer()

　　　　csv.reader()

　　　　csv.writer()

　　③读写

　　　　不用 readline读 直接使用 for line in csvReader读

　　　　使用 csv.writer.writerow()写入

2. str.replace()的实现

　　1)str.split()+str.jion(sequence)　　　　

 def myStrReplace(src,oldStr,newStr):
     return newStr.join(src.split(oldStr))

　　2)切片+递归

def myStrReplace(src,oldStr,newStr):
    pos = src.find(oldStr)
    if pos == -1:
        target = src[:]
    else:
        target = src[:pos]+newStr+src[pos+len(oldStr):]
        target = myStrReplace(target,oldStr,newStr)
    return target

3. python遍历目录，并打印.pyc 结尾的文件

 from os import walk
 for root,dir,files in walk("."):
     '''
         root,dir,files = os.walk(top[, topdown=True[, onerror=None[, followlinks=False]]])
     '''
     for file in files:
         if file.endswith(".pyc"):
             print(file)