4.8 data type conversion

4.8 Data type conversion

frequently-used 3 Type of data ：
1、Python The first data type ： character string （str）.
2、Python The second data type ： Integers （int）.
3、Python The third data type ： Floating point numbers （float）.

4.8.1 Convert to string

str( ) Converts an integer or floating-point number to a string type .

#  Set an integer variable 
number = 10 

#  take number  Convert to string 
str(number)

#  View conversion types 
type(str(number))

str

number The data type of is an integer （int）, adopt str（ ） Function to string type （str）, Using type Function to view the converted data type .

#  Set a floating point variable 
number_2 = 0.66

#  Convert a variable to a string 
str(number_2)

#  View conversion types 
type(str(number_2))

str

number_2 The data type of is originally a floating point number （float）, adopt str（ ） Function to string type （str）.

4.8.2 Convert to integer

int( ) The string 、 Convert floating point numbers to integers .

#  Set a floating point variable 
number_3 = 6.66

#  Convert variables to integers 
int(number_3)

#  View conversion types 
print(type(int(number_3)))

#  View the conversion results 
print(int(number_3))

<class 'int'>
6

When converting a floating-point number to an integer, only the number before the decimal point is retained .

#  Set a string variable 
number_4 = '66'

#  Convert variables to integers 
int(number_4)

#  View conversion types 
type(int(number_4))

int

#  Set a string variable 
number_5 = '66.66'

#  Convert variables to integers 
int(number_5)

#  View conversion types 
type(int(number_5))

---------------------------------------------------------------------------

ValueError                                Traceback (most recent call last)



ValueError: invalid literal for int() with base 10: '66.66'

Be careful

1、 Convert floating point numbers to integers ： Do not use rounding , Keep only the number before the decimal point . for example ： Floating point numbers 66.99 Convert to integer 66, instead of 67.
2、 String to integer ： Only string class data conforming to integer specification , Can be int() Coercive transformation .
for example ： character string '66.66' Can't convert to an integer , character string '66' It can be converted into an integer .

4.8.3 Convert to floating point number

float( ) The integer 、 String to float .

#  Set a string variable 
weight = '50'

#  Convert variables to floating point numbers 
float(weight)

#  View conversion types 
print(type(float(weight)))

#  View the conversion results 
print(float(weight))

<class 'float'>
50.0

#  Set an integer variable 
height = 180

#  Convert variables to floating point numbers 
float(height)

#  View conversion types 
print(type(float(height)))

#  View the conversion results 
print(float(height))

<class 'float'>
180.0

summary

1、str( )： Convert to string , There is no limit to .
2、int( )： Floating point number to the number before the reserved point ; Literal and decimal strings cannot be converted to integers .
3、float( )： Literal strings cannot be converted to floating point numbers .

Practice after class 1

The completion code , Output ： Today is my study Python Of the 100 God

#  Set a variable 
phrese_1 = ' Today is my study Python'
word_1 = ' Of the '
number_1 = 100
word_2 = ' God '

#  Output today is my study Python Of the 100 God 

Practice after class 2

The completion code , Output ： Our class has 50 people

#  Set a variable 
phrese_2 = ' Our class has '
number_2 = '50.8'
word_3 = ' people '

#  Output our class has 50 people