Many sequences of method strings apply equally well, the
However, strings are immutable, so some methods that try to change them are not available
1 String formatting
1) Formatting strings with tuples or dictionaries
format = "hello,%% enough for you?"
values = ('world','Hot')
format % values
Similar to C formatting
2) Template String
The string module provides template strings to format strings.
from string import Template
s = Template(x,gloriousx,gloriousx!)
(x = 'slurm')
Replace x with slurm
A few detailed tips to use
Formatting conversion types, field width precision, sign bit, alignment, padding, etc. Attend some manuals!
2 String method
1）find
Find substring, return leftmost index
(subs)
2)join
connection string
3）lower
4）replace
All matches are replaced
5）split
Split String Separator Not Contained
.........
..........
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The values in the dictionary are in no particular order
key can be a number, string, tuple (must be immutable, not a list)
phonebook = {'jmz':'5153','usr1':'1234','usr2':'4321'}
1) The dict function
Build dictionaries by other mappings or sequences of keys and values:
Create a dictionary with a list containing 2 tuples:
items = [('key1','value1'),('key2','value2'),('key3','value3')]
d = dict(items)
{'key1':'value1','key2':'value2','key3':'value3'} Probably not in that order.
Create dictionaries by keyword arguments:
d = dict(key1 = 'value1',key2 = 'value2',key3 = 'value3')
The above result will also be obtained
The dict function is not really a function, it is a type, similar to list, tuple, str.
2) Basic dictionary operations
Suppose d is a dictionary:
len(d) dictionary length
d[key] the value of key key in the dictionary
d[key] = value Assign value (add automatically if key does not exist)
del d[key] Delete the item whose key is key
key in d Check if it is in the dictionary
3) Dictionaries can also be used to format
Add the key (enclosed in parentheses) to each conversion descriptor (%) followed by the other descriptors:
Example: %(value)s
phonebook = {'jmz':'5153','usr1':'10086'}
"jmz's phone number is %(jmz)s." % phonebook
In this way any number of conversion descriptors can be obtained as long as the given key can be found in the dictionary.
4) Some dictionary methods
clear：
In-place operation (no return value), clears all entries in the dictionary
copy: shallow and deep copy
y = ()
y = deepcopy(x)
fromkeys：
Creates a new dictionary with the given key: the default value is None
>>>{}.fromkeys(['key1','key2'])
>>>{'key1':None,'key2':None}
Or:
>>>(['key1','key2'])
The same effect.
get：
Generally speaking, the dictionary item that the model text is good at will be wrong, for example:
>>>print d[name]
(indicates contrast)
>>>print ('name') will return None by default.
has_key:
Returns True or False
>>>d.has_key('jmz')
items and iteritems:
The items method returns the dictionary items as a list method:
d = {'key1':'value1','key2':'value2'}
>>>()
>>>[('key1','value1'),('key2','value2')]
iteritems returns an iteration over items.
>>>it = () #it is an iterator object for the above list
>>>list(it)# can convert an iterator to a list
>>>[('key1','value1'),('key2','value2')]
keys and iterkeys:
Returns the keys as a list, an iterator of the keys
pop：
('key') has a return value and removes the
popitem：
() pops up random items, since the dictionary is unordered
setdefault：
>>>('key','default_value')
When the key does not exist, return the default value and update the dictionary, if the key already exists, return its value and do not update the dictionary, which is equivalent to this sentence has no effect
update：
Use one dictionary to update another:
>>>(dd)
Add the items from dd to d and overwrite if duplicated.
values and itervalues:
Returns a list of values, an iterator over the list of values.
This above comprehensive understanding of python strings and dictionaries is all that I have shared with you.