python学习手册-ch1 to ch4

D = {'a': 1, 'b': 2, 'c': 3}
print(list(D.keys()))

for key in D:
    print(key, '=>', D[key])

f = ['a', 'f']

for key in f:
    if(not key in D):
        print('missing', key)
    if(key in D):
        print(D[key])

D = {'a': 1, 'b': 2, 'c': 3}
print(list(D.keys()))

for key in D:
    print(key, '=>', D[key])

f = ['a', 'f']

for key in f:
    if(not key in D):
        print('missing', key)
    if(key in D):
        print(D[key])

D = {'a': 1, 'b': 2, 'c': 3}
print(list(D.keys()))

for key in D:
    print(key, '=>', D[key])

f = ['a', 'f']

for key in f:
    if(not key in D):
        print('missing', key)
    if(key in D):
        print(D[key])

D = {'a': 1, 'b': 2, 'c': 3}
print(list(D.keys()))

for key in D:
    print(key, '=>', D[key])

f = ['a', 'f']

for key in f:
    if(not key in D):
        print('missing', key)
    if(key in D):
        print(D[key])

# 读写追加，只能写一种模式
file = open('a.txt','a')

file.write('hhh')

file.close()

# 写模型下不能读，要用读模式重新打开文件
read = open('a.txt')

print(read.read())
read.close()

# 用with会自动关，不用再手动close了
with open('a.txt') as read2:
    print(read2.read())