Python变量定义的简单使用介绍

variable_name = variable_name

a = 85  #将整数赋值给变量a
abc = "http://c.abc.net/"  #将字符串赋值给变量abc
abc = "http://c.efg.net/"  #修改变量的值
#将表达式的运行结果赋值给变量
sum = 100 + 200

#将 7 赋值给变量 n
n = 7
print(n)
#查看数据类型
print( type(n) )
#给x赋值一个很大的整数
x = 1111111111111111111111
print(x)
#判断x是否为int类型
print(isinstance(x,int))
#给y赋值一个很小的整数
y = -1111111111111111111111
print(y)
print( type(y) )

7
<class 'int'>
1111111111111111111111
True
<class 'int'>
-1111111111111111111111
<class 'int'>

f1 = 15.9
print("f1Value: ", f1)
print("f1Type: ", type(f1))

f2 = 0.319452585712345303
print("f2Value: ", f2)
print("f2Type: ", type(f2))

f3 = 0.0000000000000000000000000123
print("f3Value: ", f3)
print("f3Type: ", type(f3))

f4 = 31945258573194525857.12345
print("f4Value: ", f4)
print("f4Type: ", type(f4))
f6 = 15.9 * 0.1
print("f6Value: ", f6)
print("f6Type: ", type(f6))

sex = True
gender = False
print("sex: ", sex)
print("gender: ", gender)

print(True+10)
print(False+10)

"字符串内容"
'字符串内容'

str1 = '字符串1'
str2 = "字符串2"
str3 = 'I\'m a single!'
str4 = r'Ru\noob'
print(str1)
print(str2)
print(str3)
print(str4)

str5 = 'Reduce the indexing time and CPU load  \
      with pre-built Python packages shared indexes \
      Download pre-built shared indexes.'

str6 = '''Reduce the indexing time and CPU load  
      with pre-built Python packages shared indexes 
      Download pre-built shared indexes.'''

num_list = [1, 2, 3, 4, 5, 6]
language_list = ['java', "c++", "Python"]
print(num_list)
print(language_list)

age_tuple = [16, 17, 18, 19, 20]
print(age_tuple)

dict_name = {'key':'value1', 'key2':'value2', ...}

user = {'name':'皓明', 'age':18, 'sex':'男'}
print(user)
#type() 函数查看变量类型
print(type(user))

print('=====================字符串转整数=============================')
a = '345'
print(type(a))
print(type(int(a)))
print('=====================浮点数转整数=============================')
b = 3.45
print(type(b))
print(int(b))
print(type(int(b)))
print('=====================布尔值转整数=============================')
c = True
print(type(c))
print(int(c))
print(type(int(c)))
d = False
print(type(d))
print(int(d))
print(type(int(d)))

=====================字符串转整数=============================
<class 'str'>
<class 'int'>
=====================浮点数转整数=============================
<class 'float'>
3
<class 'int'>
=====================布尔值转整数=============================
<class 'bool'>
1
<class 'int'>
<class 'bool'>
0
<class 'int'>

print('=====================整数转字符串=============================')
e = 123
print(type(e))
print(str(e))
print(type(str(e)))
print('=====================浮点数转字符串=============================')
f = 1.23
print(type(f))
print(str(f))
print(type(str(f)))
print('=====================布尔值转字符串=============================')
print(str(c))
print(str(d))

print('=====================字符串转浮点数=============================')
g = '3.45'
print(type(g))
print(float(g))
print(type(float(g)))
print('=====================整数转浮点数=============================')
h = 345
print(type(h))
print(float(h))
print(type(float(h)))

print('=====================整数转布尔值=============================')
i = 2
print(type(i))
print(bool(i))
print(type(bool(i)))
j = 0
print(type(j))
print(bool(j))
print(type(bool(j)))
print('=====================字符串转布尔值=============================')
k = 'abc'
print(type(k))
print(bool(k))
print(type(bool(k)))
l = ''
print(type(l))
print(bool(l))
print(type(bool(l)))

=====================整数转布尔值=============================
<class 'int'>
True
<class 'bool'>
<class 'int'>
False
<class 'bool'>
=====================字符串转布尔值=============================
<class 'str'>
True
<class 'bool'>
<class 'str'>
False
<class 'bool'>