Note: I use PyCharm. What kind of fairy tutorial is Python crawler technology ? I love this teacher so much. But who would have thought that there is such a good introductory course in the crawler tutorial.
table of Contents:
1. Operation
Annotation
#print("hello") #第一种方法
'''
第二种方法：三个英文单引号
第三种方法：选中内容 Ctrl+/ 注释、取消注释
Ctrl加斜杠也是很多编辑器通用的注释方法
'''
run
(1) Click Run in the toolbar of the first row;
(2) Right-click the code editing area and select Run'test1'
(3) Pay attention to the lower left and upper right corners . If you create a new file that has not been run before, the two runs will not work, and the run is not the newly created file.
(4) Shortcut key Shift + F10
Description: If the shortcut key does not respond, it is not like the teacher said that your computer is not a computer used for programming. Press Fn and the shortcut key at the same time.
open a file
After File —>open or open recent, if it is the smallest unit py file, open it directly, if it is a folder, that is, the code package package, this window will appear.
This Window means to overwrite, close the current one and open a new file; New Window means to open two PyCharm at the same time.
Two, input and output
#输入：
a = input("")
b = input("请输入b:")
#输出:
print("a=",a)
print("b的值为%s。" %b)
age = 19
print("我今年%d岁"%age) #数字用%d，字符串用%s
s = "中国"
print("我的名字是%s,我的国籍是%s"%("小张",s))
print("我的名字是%s,我是%s人"%("小张","中国"))
print("www","baidu","com",sep=".")
print("hello",end="") #表示不换行
print("world",end="\t") #空格
print("python",end="\n") #换行
print("你好\n")
print("hhh")
print("\n") #反斜杠实现转义字符的功能
print(r"\n") # 加r表示直接显示原始字符串，不进行转义
print("over")
# password = input("请输入密码：")
# print("您输入的密码为：",password)
Python also has an output situation that can be called cheating:
print("a"*10)
# 输出： aaaaaaaaaa
Three, type conversion (about input)
The above code, if changed to:
age = input("")
print("我今年%d岁"%age)
It will report an error:
Because the received inout input is either a number or a text, it will be assigned to the variable as a string. Solution: Change %d to %s, or perform type conversion. (But the number will not report an error with %s)
age = input("")
print(type(age))
a = int(age)
print(type(a))
#所以可以直接写 age = int(input(""))
#同理,转字符串型 就是str()
print("a=%d"%a)
print("age=%s"%age)
Four, basic sentences
Elif:
Non-zero and non-empty values are True, 0 or None is False.
Python does not use curly braces, it is necessary to pay attention to spaces and indentation.
score = int(input("请输入成绩:\n")) #score = input("")
print("成绩为：",score)
if score >= 90 and score <= 100:
print("90-100")
elif score>=80 and score<90:
print("80-90")
elif score >= 70 and score < 80:
print("70-80")
elif score >= 60 and score < 70:
print("60-70")
else: #或 elif score <=60:
print("<=60")
for:
for i in range(5): #和range(0,5)一样
print(i,end="\t")
#0 1 2 3 4
for i in range(0,16,3): #负数也可以
print(i,end=" ")
# 0 3 6 9 12 15
name = "chengdu"
for x in name:
print(x,end="\t")
#c h e n g d u
a = ["a","b","c","d","e"]
for i in range(len(a)):
print(i,a[i],end="\t")
#0 a 1 b 2 c 3 d 4 e
while:
else can be used in conjunction with while:
count = 10
while count < 5:
print(count, "小于5")
count += 1
else:
print(count,"大于或等于5")
# 输出：
# 10大于或等于5
#求和
i = 0
sum = 0
n = 6
while i <= n:
sum += i
i += 1
print("1到%d的和为%d"%(n,sum))
# 输出：
# 1到6的和为21