[英]Replacing each character in a string using an index into a list
Suppose I have a string as follows: 假设我有一个字符串如下:
mystr = "MY VALUES ARE: (?, ?, ?, ?)"
values = ['a', 'b', 'f', 12]
I would like replace each ?
我想更换每个?
with the corresponding value at that index in the list: values
. 在列表中该索引处具有相应的值: values
。 So first ?
那么首先?
would be replaced with values[0]
, second ?
将被替换为values[0]
,第二?
would be replaced with values[1]
将被替换为values[1]
So my final str would look like: 所以我的最后一个str看起来像:
MY VALUES ARE: ('a', 'b', 'f', '12')
NOTE: The number of
?
注意:多少?
will vary but it will always equal the number of values invalues
会有所不同,但始终等于值中的values
You can replace the ?
您可以更换?
with {}
and call format
: 与{}
和呼叫format
:
print(mystr.replace("?", "'{}'").format(*values))
#MY VALUES ARE: ('a', 'b', 'f', '12')
This isn't sql, this just looks like it. 这不是sql,看起来像它。 Don't worry about SQL injection, it's not a concern here. 不必担心SQL注入,这里不必担心。
See https://bobby-tables.com/python for parametrized queries - for simply replacement use str.replace(old, new, count=1)
请参阅https://bobby-tables.com/python以进行参数化查询-只需替换即可使用str.replace(old, new, count=1)
sql = "My VALUES are (?, ?, ?, ?)"
values = ['a', 'b', 'f', 12]
for v in values:
sql = sql.replace("?",f"'{v}'",1) # inefficient - will create intermediate strings to
# be replaced
print(sql)
Output: 输出:
My VALUES are ('a', 'b', 'f', '12') 我的值是('a','b','f','12')
Slightly more performant but more code as well: 性能略高,但代码也更多:
sql = "My VALUES are (?, ?, ?, ?)"
values = ['a', 'b', 'f', 12]
k = iter(values)
# see list comp below for shorter approach
l = []
for c in sql:
if c != '?':
l.append(c)
else:
l.append(f"'{next(k)}'")
sql = "".join(l)
print(sql) # My VALUES are ('a', 'b', 'f', '12') as well
As list comprehension ( join is faster on list then on generator comps ) thx @Ev. 作为列表理解( 列表上的连接要快于生成器组件上的连接 )thx @Ev。 Kuonis : 库奥尼斯 :
sql = "".join( [ c if c != '?' else f"'{next(k)}'" for c in sql] )
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