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Python 适合开发的领域
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基本操作
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函数
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文件操作
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参考
一、Python适合开发的领域
- Web网站和各种网络服务
- 系统工具和脚本
- 作为“胶水”语言把其他语言开发的
二、基本操作
1、字符串处理
t = "He is a string. Who are you?";
print(t.capitalize()); # 将字符串的第一个字符变成大写，其余的变成小写
print(t.split()); # 分词
print(t.find('i')); # 返回第一个i的下标
print(t.find('in')); # 返回第一个in的下标
print(t.find('Python')); # 未找到时返回-1
print(t[0:4]); # 返回字符串中下标0-到3的字符
print(t.replace(' ', '|')) # 将所有空格用|代替
2、List及Tuple的用法
l = [1, 2, 3.14, 'data']
print(type(l));
m = (1, 2, 3.14, 'data')
print(type(m))
l.append([4, 3])
print(l)
l.append(m)
print(l)
l.insert(3, 'beta')
print(l)
l.remove('data')
print(l)
l.remove(m)
print(l)
3、值与地址的传递
# Python 里的 = 传递的是地址
x = [1, 2, 3, 4]
y = x
y[0] = 5
print(x)
# Python 中使用copy方法来实现值的拷贝
x = [1, 2, 3, 4]
z = x.copy()
z[0] = 5
print(x)
print(z)
4、多维表
# 多维表
a = [[1, 2, 3, 4], [1, 2, 3, 4, 5], [1, 2, 3]]
print(a)
print(a[0][3]) # 第一个子表的第四个值
5、if else
a = [24, 16, 54]
b = []
if a[0] > a[1]:
if a[0] < a[2]:
b.append(a[0])
if a[1] < a[2]:
b.append(a[1])
b.append(a[2])
else:
b.append(a[2])
b.append(a[1])
print(a)
print(b)
6、range()
for i in range(2, 10, 3): # 2到10中从2开始每个相隔3的数，前闭后开
print(i)
l = i ** 2
print(l)
a = 0
sumup = 0
while a < 100:
a += 1
sumup += a
print(sumup)
7、break & continue
for i in range(300, 351): # default step of range is 1
if i % 17 == 0:
print(i)
break
else:
print("number")
continue
三、函数
单返回值：
# Functions
def MaxOfTwo(x1, x2):
if x1 >= x2:
return x1
else:
return x2
a = 1
b = 2
c = MaxOfTwo(a, b)
print(c)
默认参数：
# Default arguments of function
def MinOfThree(x1=5, x2=10, x3=1):
if x1 < x2:
if x1 < x3:
return x1;
else:
return x3;
elif x2 < x3:
return x2
else:
return x3
print(MinOfThree())
多返回值：
# Fuction returns max and min
def MaxMinThree(x1 = 19, x2 = 6, x3 = 7):
return x1, x2
a1, b1 = MaxMinThree()
print(a1)
print(b1)
四、文件操作
1、'W'
file = open("newfile.txt", 'w')
file.write("I am created for the course . \n")
file.write("How about you? ")
file.write("How is your exam?")
file.close()
1、'W'
file = open("newfile.txt", 'w')
file.write("I am created for the course . \n")
file.write("How about you? ")
file.write("How is your exam?")
file.close()
2、'r'
file = open('newfile.txt', 'r')
# show whole file
print(file.read())
# the pointer of the file arrived end of the file, so the results of the functions below are null
file.seek(0)
# show first ten characters
print(file.read(10))
file.seek(0) # Same reason like before
# view by line
print(file.readline()) # view first line
file.seek(0) # Same reason like before
# view all by line
print(file.readlines()) # return lines list
file.close()
每次读取一行：
file = open("newfile.txt", 'r')
for line in file:
print(line)
file.close()
1、'a'
file = open("newfile.txt", 'a')
file.write("\nI am back again.\n")
file.write("Do you miss me?\n")
file.close()
file = open("newfile.txt", 'r')
print(file.read())
file.close()
