# 打开文件，用写的方式# r 表示后面字符串内容不需要转义# f 称之为文件句柄f = open(r"test01.txt", 'w')# 文件打开后必须关闭f.close()
# 此案例说明，以写方式打开文件，默认是如果没有文件，则创建

# with 语句案例
with open(r"test01.txt", 'r') as f:    pass    # 下面语句块开始对文件f进行操作    # 在本模块中不需要再使用close关闭文件f

# with 案例
with open(r"test01.txt", 'r') as f:    # 按行读取内容    strline = f.readline()    # 此结构保证能够完整读取文件直到结束    while strline:        print(strline)        strline = f.readline()

假若他日相逢，
我将何以贺你？
以眼泪，
以沉默。

# list 能用打开的文件作为参数，把文件内每一行内容作为一个元素
with open(r"test01.txt", 'r') as f:    # 以打开的文件f作为参数，创建列表    l = list(f)    for line in l:        print(line)

假若他日相逢，
我将何以贺你？
以眼泪，
以沉默。

# read 是按字符读取文件内容# 允许输入参数决定读取几个字符，如果没有指定，从当前位置读取到结尾# 否则，从当前位置读取指定个数字符
with open(r"test01.txt", 'r') as f:    strChar = f.read(1)    print(len(strChar))    print(strChar)

1假

# seek 案例# 打开文件后，从第5个字节处开始读取
# 打开读写指针在0处，即文件的开头with open(r"test01.txt", 'r') as f:    # seek 移动单位是字节    f.seek(4, 0)    strChar = f.read()    print(strChar)

他日相逢，我将何以贺你？以眼泪，以沉默。

# 关于读取文件的练习# 打开文件，三个字符一组读出内容，然后显示在屏幕上# 每读一次，休息一秒钟
# 让程序暂停，可以使用time下的sleep函数
import time
with open(r"test01.txt", 'r') as f:    # read 参数的单位是字符，可以理解成一个汉字就是一个字符    strChar = f.read(3)    while strChar:        print(strChar)        # sleep 参数单位是秒        time.sleep(1)        strChar = f.read(3)

假若他日相逢，我将何以贺你？
以眼泪，
以沉默。

# tell 函数：用来显示文件读取指针的当前位置
with open(r"test01.txt", 'r') as f:    strChar = f.read(3)    pos = f.tell()        while strChar:        print(pos)        print(strChar)                strChar = f.read(3)        pos = f.tell()        # 一下结果说明：# tell 的返回数字的单位是 byte# read 是以字节为单位

6假若他12日相逢18，我24将何以30贺你？36
以眼42泪，
48以沉默50。

# write 案例# 1. 向文件追加一行诗
# a 代表追加方式打开with open(r"test01.txt", 'a') as f:    # 注意字符串内含有换行符    f.write("生活不止眼前的苟且，\n 还有远方的苟且")

# 可以直接写入行，用writelines# writelines 表示写入很多行，参数可以是list形式with open(r"test01.txt", 'a') as f:    # 注意字符串内含有换行符    f.writelines("生活不止眼前的苟且")    f.writelines("还有远方的枸杞")

help(f.writelines)

Help on built-in function writelines:
writelines(lines, /) method of _io.TextIOWrapper instance

l = ["I", "love", "you"]with open(r"test01.txt", 'w') as f:    # 注意字符串内含有换行符    f.writelines(l)

# 序列化案例import pickle
age = 19
with open(r"test01.txt", 'wb') as f:    pickle.dump(age, f)

# 反序列化案例
import pickle
with open(r"test01.txt", 'rb') as f:    age = pickle.load(f)    print(age)

19

# 序列化案例import pickle
a = [19, 'ruochen', 'i love you', [175, 51]]
with open(r"test01.txt", 'wb') as f:    pickle.dump(a, f)

with open(r"test01.txt", 'rb') as f:    a = pickle.load(f)    print(a)

[19, 'ruochen', 'i love you', [175, 51]]

# 使用shelve创建文件并使用import shelve
# 打开文件# shv相当于一个字典shv = shelve.open(r"shv.db")
shv['one'] = 1shv['two'] = 2shv['three'] = 3
shv.close()
# 通过以上案例发现，shelve 自动创建的不仅仅是一个shv.db 文件，还包括其他格式文件

# shelve 读取案例
shv = shelve.open(r'shv.db')
try:    print(shv['one'])    print(shv['threee'])except Exception as e:        print("1")finally:    shv.close()

11

# shelve 之只读打开import shelve
shv = shelve.open(r'shv.db', flag='r')
try:    k1 = shv['one']    print(k1)finally:    shv.close()

1

import shelve

shv = shelve.open(r'shv.db')try:    shv['one'] = {"eins":1, "zwei":2, "drei":3}finally:    shv.close()    shv = shelve.open(r'shv,db')try:    one = shv['one']    print(one)finally:    shv.close()

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
D:\Anaconda3\lib\shelve.py in __getitem__(self, key)    110         try:--> 111             value = self.cache[key]    112         except KeyError:

KeyError: 'one'

During handling of the above exception, another exception occurred:

KeyError                                  Traceback (most recent call last)
<ipython-input-73-b418c9ea023b> in <module>     10 shv = shelve.open(r'shv,db')     11 try:---> 12     one = shv['one']     13     print(one)     14 finally:

D:\Anaconda3\lib\shelve.py in __getitem__(self, key)    111             value = self.cache[key]    112         except KeyError:--> 113             f = BytesIO(self.dict[key.encode(self.keyencoding)])    114             value = Unpickler(f).load()    115             if self.writeback:

D:\Anaconda3\lib\dbm\dumb.py in __getitem__(self, key)    151             key = key.encode('utf-8')    152         self._verify_open()--> 153         pos, siz = self._index[key]     # may raise KeyError    154         with _io.open(self._datfile, 'rb') as f:    155             f.seek(pos)

KeyError: b'one'

# shelve 忘记写回，需要使用强制写回shv = shelve.open(r"shv.db")try:    k1 = shv['one']    print(k1)    # 此时，一旦shelve关闭，则内容还是存在于内存中，没有写回数据库    k1["eins"] = 100finally:    shv.close()    shv = shelve.open(r"shv.db")try:    k1 = shv['one']    print(k1)finally:    shv.close()

{'eins': 1, 'zwei': 2, 'drei': 3}{'eins': 1, 'zwei': 2, 'drei': 3}

# shelve 忘记写回，需要使用强制写回shv = shelve.open(r"shv.db", writeback=True)try:    k1 = shv['one']    print(k1)    # 此时，一旦shelve关闭，则内容还是存在于内存中，没有写回数据库    k1["eins"] = 100finally:    shv.close()    shv = shelve.open(r"shv.db")try:    k1 = shv['one']    print(k1)finally:    shv.close()

{'eins': 1, 'zwei': 2, 'drei': 3}{'eins': 100, 'zwei': 2, 'drei': 3}

# shelve 使用with管理上下文环境
with shelve.open(r'shv.db', writeback=True) as shv:    k1 = shv['one']    print(k1)    k1['eins'] = 1000    with shelve.open(r"shv.db") as shv:    print(shv['one'])

{'eins': 100, 'zwei': 2, 'drei': 3}{'eins': 1000, 'zwei': 2, 'drei': 3}