python27 文件读写

‘‘‘r-读 文件不存在报错FileNotFoundError‘‘‘
try:
    f = open(‘file0.txt‘,‘r‘)
    content = f.readlines()
except FileNotFoundError:
    content = None
print(content)

‘‘‘w-写 文件不存在创建；文件存在清除内容；重新写入‘‘‘
f = open(‘file1.txt‘,‘w‘)
f.write(‘first line111\nsecond line111‘)
f.close()

f = open(‘file1.txt‘,‘w‘)
f.write(‘first line222\nsecond line222‘)
f.close()

f = open(‘file1.txt‘,‘r‘)
print(f.read())
print(f.readlines()) #到文档结尾了 空
f.seek(0) #移到文档开头
print(f.readlines()) #可以读取内容
f.close()

‘‘‘a-追加 文件不存在报错；在最后追加内容‘‘‘
f = open(‘file1.txt‘,‘a‘)
f.write(‘\n #third line 222\n\n555‘) #追加
f.close()

f = open(‘file1.txt‘,‘r‘)
print([ line.strip() for line in f.readlines()]) #去掉换行符
f.close()

‘‘‘w+ r+ 读写。w+文件不存在创建；r+文件不存在报错。 同时可读写容易出错，需要移动指针。建议只读或只写‘‘‘
f = open(‘file1.txt‘,‘r+‘)
lines = f.readlines()
lines[0] = ‘#第一行w+文件不存在创建；r+文件不存在报错。建议只读或只写w+ r+ 读写\n‘ # 与原第一行字数不同
f.seek(0)
f.writelines(lines)
f.seek(0)
print(f.readlines())  #第三行内容不对


f = open(‘file1.txt‘,‘w+‘)
f.writelines(lines)
print(f.readlines()) #这样对了。
f.close()

‘‘‘b 二进制‘‘‘
f = open(‘file1.txt‘,‘rb‘)
print(f.read())
f.close()

‘‘‘with使用完自动关闭‘‘‘
with open(‘file1.txt‘,‘r‘) as f:
    for line in f.readlines():
        print(line.strip()) #去除换行符

‘‘‘显示文件的所有行 忽略以#开头的‘‘‘
with open(‘file1.txt‘,‘r‘) as f:
    for line in f.readlines():
        if not line.startswith(‘#‘):
            print(line.strip())

‘‘‘处理#前面的空格‘‘‘
with open(‘file1.txt‘,‘r‘) as f:
    lines = f.readlines()
    for i in range(len(lines)):
        if lines[i].strip().startswith(‘#‘) and (not lines[i].startswith(‘#‘)):
            lines[i] = lines[i].strip()
with open(‘file1.txt‘,‘w‘) as f:
    f.writelines(lines)

‘‘‘显示文件的前N行‘‘‘
N = 2
file = ‘file1.txt‘
with open(file,‘r‘) as f:
    for i in range(N):
        print(f.readline().strip())

‘‘‘显示文件总行数‘‘‘
with open(file,‘r‘) as f:
    print(‘总行数：‘,len(f.readlines()))

‘‘‘每次显示文件的2行‘‘‘
file = input(‘filename‘)
with open(file,‘r‘) as f:
    lines = f.readlines()
    f.seek(0)
    pages = int(len(lines)/2 if len(lines)%2 == 0 else len(lines)/2+1) #总页数
    page = 0 #页码
    count = 0 #行数
    if page < pages:
        print(‘第%d页‘%(page+1))
        for i in range(2):
            if count < len(lines):
                line = lines[count]
                print(‘第%d行：%s‘%((count+1),line.strip()))
                count += 1
            else:
                print(‘数据已显示完‘)
                break
        page += 1
    while page < pages:
        key = input(‘enter any key to continue...‘)
        print(‘第%d页‘ % (page + 1))
        for i in range(2):
            if count < len(lines):
                line = lines[count]
                print(‘第%d行：%s‘ % ((count + 1), line.strip()))
                count += 1
            else:
                print(‘数据已显示完‘)
                break
        page += 1