> filter(methodcaller('isalpha'), strs)īut this isn't very straightforward, that's why it's nice to just use list comprehensions to avoid this trouble. One alternative is to use methodcaller > strs =
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lambda is the keyword used for defining the lambda function. myFunction lambda arguments: expression Here, myFunction is the name of the lambda function that will be created using this statement. The syntax for declaring a lambda function is as follows. You could simply change this to unicode.isalpha but if you are mixing unicode and str you need something cross compatible. We define a lambda function using the lambda keyword in python. Therefore the clean solution using str.isalpha won't work. Unfortunately python 2.x has two different string types (In python 3 there is only str which is unicode) str and unicode. This makes it clean and fast to use filter here, but remember the consequences once you involve lambdas. This function directly changes the behavior of the key function itself. Many people have suggested > filter(lambda s: s.isalpha(), strs)īut remember lambda s: s.isalpha() is just fluff for str.isalpha, the method of the string class. In Python, key functions are higher-order functions that take another function (which can be a lambda function) as a key argument. In : %timeit if s.isalpha() else s for s in strs]ġ000000 loops, best of 3: 799 ns per loop In : %timeit map(lambda s: s if s.isalpha() else s, strs)ġ000000 loops, best of 3: 1.48 us per loop Then why would you use map? map is fast and good looking for simple cases: > map(str.upper, strs)īut the instance you have to use lambda, map becomes ugly and slow.
![python lambda python lambda](http://chenweixiang.github.io/assets/Python_Operators.png)
Similarly, the lambda keyword is used to define an anonymous function in Python. As we already know that the def keyword is used to define a normal function in Python. They are the most adaptable and in most cases, the most readable way of doing this. Python Lambda Functions are anonymous function means that the function is without a name.
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Firstly, become accustomed to list comprehensions: > strs =