Python最常用的函数、基础语句有哪些？

作者 |?朱卫军

来源 |?Python大数据分析

一、内置函数

内置函数是python自带的函数方法，拿来就可以用，比方说zip、filter、isinstance等。

下面是Python官档给出的内置函数列表，相当的齐全。

下面几个是常见的内置函数：

1、enumerate(iterable,start=0)

seasons?=?['Spring',?'Summer',?'Fall',?'Winter']
list(enumerate(seasons))
[(0,?'Spring'),?(1,?'Summer'),?(2,?'Fall'),?(3,?'Winter')]
list(enumerate(seasons,?start=1))
[(1,?'Spring'),?(2,?'Summer'),?(3,?'Fall'),?(4,?'Winter')]

2、zip(*iterables,strict=False)

>>>?for?item?in?zip([1,?2,?3],?['sugar',?'spice',?'everything?nice']):
...?????print(item)
...
(1,?'sugar')
(2,?'spice')
(3,?'everything?nice')

3、filter(function,iterable)

def?is_even(x):
????if?x?%?2?==?0:
????????return?True
????else:
????????return?False

然后使用filter对某个列表进行筛选：

l1?=?[1,?2,?3,?4,?5]
fl?=?filter(is_even,?l1)
list(fl)

4、isinstance(object,classinfo)

「isinstance」是用来判断某一个变量或者是对象是不是属于某种类型的一个函数

如果参数object是classinfo的实例，或者object是classinfo类的子类的一个实例， 返回True。如果object不是一个给定类型的的对象， 则返回结果总是False

>>>a?=?2
>>>?isinstance?(a,int)
True
>>>?isinstance?(a,str)
False
>>>?isinstance?(a,(str,int,list))????#?是元组中的一个返回?True
True

5、eval(expression[,globals[,locals]])

>>>x?=?7
>>>?eval(?'3?*?x'?)
21
>>>?eval('pow(2,2)')
4
>>>?eval('2?+?2')
4
>>>?n=81
>>>?eval("n?+?4")
85

常用句式

「1、format字符串格式化」

#?格式化字符串
print('{}?{}'.format('hello','world'))?

#?浮点数
float1?=?563.78453
print("{:5.2f}".format(float1))

「2、连接字符串」

string1?=?"Linux"
string2?=?"Hint"
joined_string?=?string1?+?string2
print(joined_string)

「3、if...else条件语句」

#?Assign?a?numeric?value
number?=?70

#?Check?the?is?more?than?70?or?not
if?(number?>=?70):
????print("You?have?passed")
else:
????print("You?have?not?passed")

「4、for...in、while循环语句」

#?Initialize?the?list
weekdays?=?["Sunday",?"Monday",?"Tuesday","Wednesday",?"Thursday","Friday",?"Saturday"]
print("Seven?Weekdays?are:\n")
#?Iterate?the?list?using?for?loop
for?day?in?range(len(weekdays)):
????print(weekdays[day])

while循环

#?Initialize?counter
counter?=?1
#?Iterate?the?loop?5?times
while?counter?<?6:
????#?Print?the?counter?value
????print?("The?current?counter?value:?%d"?%?counter)
????#?Increment?the?counter
????counter?=?counter?+?1

「5、import导入其他脚本的功能」

#?Initialize?values
vacation1?=?"Summer?Vacation"
vacation2?=?"Winter?Vacation"

#?Import?another?python?script
import?vacations?as?v

#?Initialize?the?month?list
months?=?["January",?"February",?"March",?"April",?"May",?"June",
??????????"July",?"August",?"September",?"October",?"November",?"December"]
#?Initial?flag?variable?to?print?summer?vacation?one?time
flag?=?0

#?Iterate?the?list?using?for?loop
for?month?in?months:
????if?month?==?"June"?or?month?==?"July":
????????if?flag?==?0:
????????????print("Now",v.vacation1)
????????????flag?=?1
????elif?month?==?"December":
????????????print("Now",v.vacation2)
????else:
????????print("The?current?month?is",month)

「6、列表推导式」

#?Create?a?list?of?characters?using?list?comprehension
char_list?=?[?char?for?char?in?"linuxhint"?]
print(char_list)

#?Define?a?tuple?of?websites
websites?=?("google.com","yahoo.com",?"ask.com",?"bing.com")

#?Create?a?list?from?tuple?using?list?comprehension
site_list?=?[?site?for?site?in?websites?]
print(site_list)

「7、读写文件」

#Assign?the?filename
filename?=?"languages.txt"
#?Open?file?for?writing
fileHandler?=?open(filename,?"w")

#?Add?some?text
fileHandler.write("Bash\n")
fileHandler.write("Python\n")
fileHandler.write("PHP\n")

#?Close?the?file
fileHandler.close()

#?Open?file?for?reading
fileHandler?=?open(filename,?"r")

#?Read?a?file?line?by?line
for?line?in?fileHandler:
??print(line)

#?Close?the?file
fileHandler.close()

「8、切片和索引」

形如列表、字符串、元组等序列，都有切片和索引的需求，因为我们需要从中截取数据，所以这也是非常核心的技能。

var1?=?'Hello?World!'
var2?=?"zhihu"

print?("var1[0]:?",?var1[0])
print?("var2[1:5]:?",?var2[1:5])

「9、使用函数和类」

#?Define?addition?function
def?addition(number1,?number2):
????result?=?number1?+?number2
????print("Addition?result:",result)

#?Define?area?function?with?return?statement
def?area(radius):
????result?=?3.14?*?radius?*?radius
????return?result??

#?Call?addition?function
addition(400,?300)
#?Call?area?function
print("Area?of?the?circle?is",area(4))

#?Define?the?class
class?Employee:
????name?=?"Mostak?Mahmud"
????#?Define?the?method
????def?details(self):
????????print("Post:?Marketing?Officer")
????????print("Department:?Sales")
????????print("Salary:?$1000")

#?Create?the?employee?object????
emp?=?Employee()
#?Print?the?class?variable
print("Name:",emp.name)
#?Call?the?class?method
emp.details()

「10、错误异常处理」

#?Try?block
try:
????#?Take?a?number
????number?=?int(input("Enter?a?number:?"))
????if?number?%?2?==?0:
????????print("Number?is?even")
????else:
????????print("Number?is?odd")

#?Exception?block????
except?(ValueError):
??#?Print?error?message
??print("Enter?a?numeric?value")

小结

分享

点收藏

点点赞

点在看

关注公众号：拾黑（shiheibook）了解更多

[广告]赞助链接：

四季很好，只要有你，文娱排行榜：https://www.yaopaiming.com/
让资讯触达的更精准有趣：https://www.0xu.cn/