python语法31[基本数据类型和流程控制]
2013-03-24 19:22
921 查看
所有类型如下图:
![](http://images.cnblogs.com/cnblogs_com/itech/pythonperl/pythondata.png)
一 基础数据类型
1)数字类型
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> 2/2+2*2
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
5.0
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> (50-5*6)/4
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
5.0
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> 8/5
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
1.6
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> 8//5
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
1
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> x=y=1.5
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> x*y
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
2.25注意:/表示先转化为double然后在除运算,但是//表示不进行double的转化,相当于两个整数相除。
2)string类型
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> 'hello world'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
'hello world'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> "hello world"
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
'hello world'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> "doesn't"
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
"doesn't"
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> 'hello "tom"'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
'hello "tom"'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> "hello,\"tom\""
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
'hello,"tom"'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> hello="hello,\
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
i miss you."
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> print(hello)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
hello,i miss you.
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> print(r"hello\n world")
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
hello\n world
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> word='hello'+'A'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> print(word)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
helloA
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> word[0:5]+'B'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
'helloB'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> word[-1]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
'A'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> len(word)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
6注意:
单引号''和双引号""作用相同,都用来表示字符串,但是单引号''中可以有双引号"",双引号""中也可以有单引号'',但是如果双引号""中使用双引号""或是单引号''中使用单引号''时,必须使用转义字符\,例如\'或\"。
行末尾\表示字符串换行。
字符串前的r表示纯字符串,此时字符串中的转义字符失效。
+表示字符串的链接。
[]可以用来索引字符串中的字符,但是不能用来修改字符串中的字符。
len()用来获得字符串的长度。
3)List
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a = ['money', 'money', 'money', 100000000]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
['money', 'money', 'money', 100000000]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a[3]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
100000000
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a[-1] = a[-1] * 2
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a[-1]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
200000000
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> ['i', 'want'] + a
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
['i', 'want', 'money', 'money', 'money', 200000000]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
['money', 'money', 'money', 200000000]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a[:0] = ['i', 'want']
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
['i', 'want', 'money', 'money', 'money', 200000000]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a[2:4] = []
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
['i', 'want', 'money', 200000000]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> len(a)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
4
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a[:]= []
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
[]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>>
注意:
list中可以包含任何不同的数据类型。
[]可以修改list中的元素。
+可以用来list的合并。
=[]可以用来删除list中某些元素。
len可以用来获得list的长度。
二 流程控制关键字
注意:Python中使用冒号:和语句前的空格对其齐表示其他语言中的{和}所表示的语句块的开始和结束。
1)if/else
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
x = int(input("Please enter an integer: "))
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
if x < 0:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
x = 0
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print('Negative changed to zero')
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
elif x == 0:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print('Zero')
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
elif x == 1:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print('Single')
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
else:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print('More')
2)for
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
a = ['cat', 'window', 'defenestrate']
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
for x in a[1:]:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print(x, len(x))
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
if len(x) > 6: a.insert(0, x)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print(a)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
b = ['Mary', 'had', 'a', 'little', 'lamb']
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
for i in range(len(b)):
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print(i, b[i])
3)while
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
a, b = 0, 1
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
while b < 10:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print(b)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
a, b = b, a+b
4)Continue/Break/Pass
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
for i in range(100):
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
if(i%5 == 0):
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print(i);
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
continue;
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
elif(i >= 50):
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print("over");
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
break;
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
else:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
pass;
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print("thanks")注意:pass相当于一条空语句。
![](http://images.cnblogs.com/cnblogs_com/itech/pythonperl/pythondata.png)
一 基础数据类型
1)数字类型
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> 2/2+2*2
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
5.0
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> (50-5*6)/4
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
5.0
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> 8/5
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
1.6
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> 8//5
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
1
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> x=y=1.5
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> x*y
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
2.25注意:/表示先转化为double然后在除运算,但是//表示不进行double的转化,相当于两个整数相除。
2)string类型
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> 'hello world'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
'hello world'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> "hello world"
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
'hello world'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> "doesn't"
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
"doesn't"
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> 'hello "tom"'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
'hello "tom"'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> "hello,\"tom\""
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
'hello,"tom"'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> hello="hello,\
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
i miss you."
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> print(hello)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
hello,i miss you.
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> print(r"hello\n world")
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
hello\n world
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> word='hello'+'A'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> print(word)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
helloA
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> word[0:5]+'B'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
'helloB'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> word[-1]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
'A'
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> len(word)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
6注意:
单引号''和双引号""作用相同,都用来表示字符串,但是单引号''中可以有双引号"",双引号""中也可以有单引号'',但是如果双引号""中使用双引号""或是单引号''中使用单引号''时,必须使用转义字符\,例如\'或\"。
行末尾\表示字符串换行。
字符串前的r表示纯字符串,此时字符串中的转义字符失效。
+表示字符串的链接。
[]可以用来索引字符串中的字符,但是不能用来修改字符串中的字符。
len()用来获得字符串的长度。
3)List
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a = ['money', 'money', 'money', 100000000]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
['money', 'money', 'money', 100000000]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a[3]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
100000000
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a[-1] = a[-1] * 2
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a[-1]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
200000000
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> ['i', 'want'] + a
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
['i', 'want', 'money', 'money', 'money', 200000000]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
['money', 'money', 'money', 200000000]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a[:0] = ['i', 'want']
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
['i', 'want', 'money', 'money', 'money', 200000000]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a[2:4] = []
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
['i', 'want', 'money', 200000000]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> len(a)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
4
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a[:]= []
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>> a
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
[]
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
>>>
注意:
list中可以包含任何不同的数据类型。
[]可以修改list中的元素。
+可以用来list的合并。
=[]可以用来删除list中某些元素。
len可以用来获得list的长度。
二 流程控制关键字
注意:Python中使用冒号:和语句前的空格对其齐表示其他语言中的{和}所表示的语句块的开始和结束。
1)if/else
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
x = int(input("Please enter an integer: "))
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
if x < 0:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
x = 0
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print('Negative changed to zero')
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
elif x == 0:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print('Zero')
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
elif x == 1:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print('Single')
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
else:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print('More')
2)for
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
a = ['cat', 'window', 'defenestrate']
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
for x in a[1:]:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print(x, len(x))
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
if len(x) > 6: a.insert(0, x)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print(a)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
b = ['Mary', 'had', 'a', 'little', 'lamb']
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
for i in range(len(b)):
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print(i, b[i])
3)while
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
a, b = 0, 1
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
while b < 10:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print(b)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
a, b = b, a+b
4)Continue/Break/Pass
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
for i in range(100):
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
if(i%5 == 0):
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print(i);
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
continue;
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
elif(i >= 50):
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print("over");
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
break;
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
else:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
pass;
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
print("thanks")注意:pass相当于一条空语句。
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