详解Python输出

 flush/end/swp

#print("hello world",flush=True)

print("test print!!!",end=" ")
print("no wrap")

flush代表刷新缓冲区

end" " 代表去空格

print("string "," string 2" ,1003,sep=",")

sep指定用什么分割

标准错误流

print("error out",file=sys.stderr)

 往文件里写

往标准文件里写

logf=open("log.txt","a")
print("Log to file ",file=logf)
logf.close()

写入Excel的csv格式文件

csv=open("python.csv","a")
print("名称","数量","内容",sep=",",file=csv)
print("name1","1","1111",sep=",",file=csv)
print("name2","2","2222",sep=",",file=csv)
csv.close()

Python中的复数

num = 1+2j
print(num.imag)
print(num.real)
num=complex(1,2)
print(num)
print(type(num))
print(id(num))

Python中的字符串

print("test string")
str1="test strinq001"
print(str1)
print(type(str1))
print(id(str1))

print(str1[2])
print(str1[3])

 截取串

str1="0123456"
print(str1[3:6])
print(str1[-3:-1])
print(str1[1])

str[-1]=6;

负数表示从结尾开始。

r/R可以消除转义字符

print(r"DDDD\t\ssfsa")

字符串拼接

a="aaaaaaaa"\
    "bbbbbbbbb"\
    "ccccccccc"
print(a)
a=("aaaaaaaa\
bbbbbb\
cccccc"
   )
print(a)
a=""" 
    aaaaaaaaa
    BBBBBBBBB
    CCCCCCCCc
"""
print(a)

‘’‘

代表注释

‘’’

str1="xxx"
str2="yyy"
str3=str1+str2;
print(str3)

str1="xxx"
str2="yyy"
str3=str1+str2;
print(str3)
s="格式化字符串 %s %d %c %f " % ("teststr",200,str1[0],1.0)
print(s)
print(len(s))

汉字和英文都是一个字节

元组 Tuple

指向不能更改其余和list相似

tuple = ("str1","str2")
#元祖指向不可改变
try:
    tuple[0]="000"
except TypeError:
    print("元祖指向不可改变")
#元祖指向的值可以改
tup = ("str1","str2",1,[1,2,3])
tup[3][0]=100
print(tup)

字典：

#dictionary 初始化
dic={"name": "python",
     "year": 1991,
     "ver": 3.7,
     4: 5,
     "keys" : ["print","for"]
}
print(dic)
dic[4]=6
dic["src"]="c"
print(dic)
dic.pop("keys")
print(dic)
dic.clear()

判断关键字是否存在通过抛异常

try:
     print(dic["name"])
     print(dic["arg"])
except KeyError:
     print("dic KeyError")
if "year" in dic:
     print("key year")