python学习记录（一）

>>> print('hello')

hello

>>> print(1+2)

3

print(1+2+'')

Traceback (most recent call last):

  File "<pyshell#2>", line 1, in <module>

    print(1+2+'')

TypeError: unsupported operand type(s) for +: 'int' and 'str' #整数与字符串不能相加

>>> print('hello'*7)

hellohellohellohellohellohellohello #整数能与字符串相乘

>>> print('hello'*7.0)

Traceback (most recent call last):

  File "<pyshell#4>", line 1, in <module>

    print('hello'*7.0)

TypeError: can't multiply sequence by non-int of type 'float' #浮点数不能与字符串相乘

>>> print(int("") + int(""))

5

>>> float(input("num1:"))+float(input("num2:"))

num1:30

num2:2

32.0

int(input("num1:"))

num1:2.0

Traceback (most recent call last):

  File "<pyshell#7>", line 1, in <module>

    int(input("num1:"))

ValueError: invalid literal for int() with base 10: '2.0' #输入为浮点数，与int不符

>>> float(""*int(input("enter a number:")))

enter a number:2

210210.0 #210210转化为浮点型

>>> a=1

>>> print(a)

1

>>> print(a+3)

4

>>> print(a*2)

2

>>> a="hello"

>>> print(a*2)

hellohello

>>> del a

>>> print(a)

Traceback (most recent call last):

  File "<pyshell#20>", line 1, in <module>

    print(a)

NameError: name 'a' is not defined

>>> a = input("number:")

number:2

>>> print(a)

2

>>> a=1

>>> a+=2

>>> print(a)

3

>>> str1="abc"

>>> str1+="def"

>>> print(str1)

abcdef