Python crawler Lecture 1

Python Environmental installation

• Python Installation of interpreter
• PyCharm Installation

Python Basics

1. I / O statement ：

Output *print()* It's a python Built in functions , You can output the objects in brackets directly .

print('hello')
# result 
>>> hello

*print()* You can also print multiple strings

age = 1
name = " Li Bai "
school = " Shenyang Institute of technology "
print(name, age, school) # Separated by commas 
# result 
>>> Li Bai 1 Shenyang Institute of technology

Input *input()* also python Built in functions

name = input(" Please enter a name ：") # The words in parentheses are reminders 
print(name)
# result 
>>> Please enter a name ： Li Bai
>>> Li Bai

2. Common data types

Common data types are numbers 、 list 、 character string 、 Dictionaries 、 Tuples 、 aggregate .

list ：

Create a list

heroList = [' Ruban 7 ', " Angela ", " Li Bai ", ' Hou Yi ', 100, 10.1]
print(heroList)
# result 
>>> [' Ruban 7 ', ' Angela ', ' Li Bai ', ' Hou Yi ', 100, 10.1]

Accessing elements in a list ---- List name [ Indexes ]

print(" Hero for ：",heroList[1],heroList[0])
# result 
>>> Hero for ： Angela Ruban 7

Additive elements ----append Is to add elements at the end of the list

heroList.append(' Ruban master ')
print(' List after adding ', heroList)
# result 
>>> List after adding [' Ruban 7 ', ' Angela ', ' Li Bai ', ' Hou Yi ', 100, 10.1, ' Ruban master ']

Modifying elements

heroList[4] = " The sable cicada "
print(" Modified list ", heroList)
# result 
>>> Modified list [' Ruban 7 ', ' Angela ', ' Li Bai ', ' Hou Yi ', ' The sable cicada ', 10.1, ' Ruban master ']

Remove elements

del heroList[5]
print(" Deleted list ", heroList)
# result 
>>> Deleted list [' Ruban 7 ', ' Angela ', ' Li Bai ', ' Hou Yi ', ' The sable cicada ', ' Ruban master ']

3. The branch of judgment

if-else sentence

age = input(' Please enter your age ：') # Enter the age 
print(type(age)) # Determine the type of variable is type function 
age = int(age) # Convert to numeric type int
print(type(age))
if age >= 18: # Judge the condition 
print(" Congratulations on your adulthood , You can go to the Internet bar ")
else:
print('sorry, You're still a baby ')
# Older than or equal to 18, result 
Please enter your age ：18
<class 'str'>
<class 'int'>
Congratulations on your adulthood , You can go to the Internet bar
# Older than 18, result 
Please enter your age ：3
<class 'str'>
<class 'int'>
sorry, You're still a baby