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))
