模块七 python输入与输出

字面量

以变量或常量给出的原始数据

字面量类型：

数值型

字符型

布尔型

字面量集合：列表，元组，字典，集合

特殊字面量：None

字面量插值

将变量，常量以及表达式插入的一种技术，他可以避免字符串拼接的问题

3种方法

1 格式化

%的用法

>>> name = "lili"
>>> print("my name is %s" %name)
my name is lili

 

>>> name = "lili"
>>> print("my name is %s" %name)
my name is lili
>>> age = 10
>>> print("my name is %s,my age is %d" %(name,age))
my name is lili,my age is 10
>>>

　

>>> name = "lili"
>>> print("my name is %s" %name)
my name is lili
>>> age = 10
>>> print("my name is %s,my age is %d" %(name,age))
my name is lili,my age is 10
>>> print("my name is %s,my age is %d,num is %f" %(name,age,3.34444))
my name is lili,my age is 10,num is 3.344440
>>>

　　

　

>>> print("my name is %s,my age is %d,num is %.2f" %(name,age,3.34444))
my name is lili,my age is 10,num is 3.34
>>>

　

name = "lili"
age = 90
list1 = [1,2,3,4]
dic1 = {"a":"fo","b":"c"}
print("my name is {0},age is {1}".format(name,age))
print("my name is {1},age is {0} {1}{0}{0}".format(name,age))

print("my list is {},my dic is {}".format(list1,dic1))　　

 

2 format（）方法

用法：str.format()可以将

字符串

列表

字段

name = "lili"
print("my name is {}".format(name))

　

name = "lili"
age = 90
print("my name is {},age is {}".format(name,age))

　　

　

name = "lili"
age = 90
print("my name is {0},age is {1}".format(name,age))
print("my name is {1},age is {0}".format(name,age))

　输出结果

D:\py\test\venv\Scripts\python.exe "D:/py/test/拉勾-第三阶段/模块7 输入与输出.py"
my name is lili,age is 90
my name is 90,age is lili

　列表的解包，需要加*　

# name = ["lili","tom","jerry"]
# print("we name is {}、{} and {}".format(*name))

 

#字典的解包，需要加**
#用法print("my name is {key值},my age is {key值}".format(**dic))
dic = {"name":"lili","age":44}
print("my name is {name},my age is {age}".format(**dic))

　　3 F-strings 字符串格式化机制

使用方法：f'{变量名}

注意：大括号里面可以是表达式或者函数

大括号内不能转移，不能使用\

list = ["lili","tom","jerry"]
name = "lili"
dic = {"name":"lili","age":44}

print(f"my name is {name},my list is {list},my dic is {dic}")

输出结果

D:\py\test\venv\Scripts\python.exe "D:/py/test/拉勾-第三阶段/模块7 输入与输出.py"
my name is lili,my list is ['lili', 'tom', 'jerry'],my dic is {'name': 'lili', 'age': 44}

　　#可以插入表达式

list = ["lili","tom","jerry"]
name = "abcdef"
dic = {"name":"lili","age":44}

print(f"my name is {name.upper()},my list is {list},my dic is {dic}")

　　如果表达式有：之类的特殊字符，需要加一个（）

print(f"resule is {(lambda x : x+1)(2)}")

　　输出结果

resule is 3

　　

文件的读取

操作步骤

1 打开文件，获取文件描述符

2 操作文件描述符读，写

3 关闭文件

注意：

文件读写错操作完成后，应该及时关闭

open()

 

 

 with  语句块，可以将文件打开之后，操作完毕，自动关闭这个文件

图片的读取需要使用rb，读取二进制的格式

正常的文本，可以使用rt，也就是它的默认格式即可

 

with open("date.txt") as f:
    print(f.readlines())

　输出结果

D:\py\test\venv\Scripts\python.exe D:/py/test/拉勾-第三阶段/文件的读写.py
['1\n', 'd\n', '4\n', 'g\n', 'v\n', 'g\n', 'hdhddkkdkddldkd']

　

with open("date.txt") as f:
    while True:
        line = f.readline()
        if line:
            print(line)
        else:
            break

　　

json格式转化

 

 

import  json
dic = {
    "name":["jerry","ladddd"],
    "age":20
}
print(type(dic))
dic2 = json.dumps(dic)# dumps讲json转换成字符串的格式
print(dic2)
print(type(dic2))
dic3 = json.loads(dic2)#loads讲字符串转换成dict形式
print(type(dic3))